diff --git a/lib/std/core/allocators/arena_allocator.c3 b/lib/std/core/allocators/arena_allocator.c3
index f96be7373..20489a3dd 100644
--- a/lib/std/core/allocators/arena_allocator.c3
+++ b/lib/std/core/allocators/arena_allocator.c3
@@ -2,14 +2,14 @@ module std::core::mem::allocator;
 
 struct ArenaAllocatorHeader
 {
-	usize size;
+	usz size;
 	char[*] data;
 }
 /**
  * @require !alignment || math::is_power_of_2(alignment)
  * @require data `unexpectedly missing the allocator`
  */
-private fn void*! arena_allocator_function(Allocator* data, usize size, usize alignment, usize offset, void* old_pointer, AllocationKind kind)
+private fn void*! arena_allocator_function(Allocator* data, usz size, usz alignment, usz offset, void* old_pointer, AllocationKind kind)
 {
 	ArenaAllocator* arena = (ArenaAllocator*)data;
 	bool clear = false;
@@ -63,14 +63,14 @@ private fn void*! arena_allocator_function(Allocator* data, usize size, usize al
  * @require mem::aligned_offset(offset, ArenaAllocatorHeader.alignof) == offset
  * @require this != null
  **/
-private fn void*! ArenaAllocator._alloc(ArenaAllocator* this, usize size, usize alignment, usize offset)
+private fn void*! ArenaAllocator._alloc(ArenaAllocator* this, usz size, usz alignment, usz offset)
 {
-	usize total_len = this.data.len;
+	usz total_len = this.data.len;
 	if (size > total_len) return AllocationFailure.CHUNK_TOO_LARGE!;
     void* start_mem = this.data.ptr;
 	void* unaligned_pointer_to_offset = start_mem + this.used + ArenaAllocatorHeader.sizeof + offset;
 	void* aligned_pointer_to_offset = mem::aligned_pointer(unaligned_pointer_to_offset, alignment);
-	usize end = (usize)(aligned_pointer_to_offset - this.data.ptr) + size - offset;
+	usz end = (usz)(aligned_pointer_to_offset - this.data.ptr) + size - offset;
 	if (end > total_len) return AllocationFailure.OUT_OF_MEMORY!;
 	this.used = end;
 	void *mem = aligned_pointer_to_offset - offset;
@@ -89,13 +89,13 @@ private fn void*! ArenaAllocator._alloc(ArenaAllocator* this, usize size, usize
  * @require mem::aligned_offset(offset, ArenaAllocatorHeader.alignof) == offset
  * @require this != null
  **/
-private fn void*! ArenaAllocator._realloc(ArenaAllocator* this, void *old_pointer, usize size, usize alignment, usize offset)
+private fn void*! ArenaAllocator._realloc(ArenaAllocator* this, void *old_pointer, usz size, usz alignment, usz offset)
 {
 	assert(old_pointer >= this.data.ptr, "Pointer originates from a different allocator.");
-	usize total_len = this.data.len;
+	usz total_len = this.data.len;
 	if (size > total_len) return AllocationFailure.CHUNK_TOO_LARGE!;
 	ArenaAllocatorHeader* header = old_pointer - ArenaAllocatorHeader.sizeof;
-	usize old_size = header.size;
+	usz old_size = header.size;
 	// Do last allocation and alignment match?
 	if (&this.data[this.used] == old_pointer + old_size && mem::ptr_is_aligned(old_pointer + offset, alignment))
 	{
@@ -105,7 +105,7 @@ private fn void*! ArenaAllocator._realloc(ArenaAllocator* this, void *old_pointe
         }
         else
         {
-	        usize new_used = this.used + size - old_size;
+	        usz new_used = this.used + size - old_size;
             if (new_used > total_len) return AllocationFailure.OUT_OF_MEMORY!;
             this.used = new_used;
         }
diff --git a/lib/std/core/allocators/dynamic_arena.c3 b/lib/std/core/allocators/dynamic_arena.c3
index 0fa46975b..4d0f10794 100644
--- a/lib/std/core/allocators/dynamic_arena.c3
+++ b/lib/std/core/allocators/dynamic_arena.c3
@@ -4,14 +4,14 @@ private struct DynamicArenaPage
 {
 	void* memory;
 	void* prev_arena;
-	usize total;
-	usize used;
+	usz total;
+	usz used;
 	void* last_ptr;
 }
 
 private struct DynamicArenaChunk
 {
-	usize size;
+	usz size;
 }
 
 /**
@@ -23,7 +23,7 @@ private fn void DynamicArenaAllocator.free(DynamicArenaAllocator* this, void* pt
 	DynamicArenaPage* current_page = this.page;
 	if (ptr == current_page.last_ptr)
 	{
-		current_page.used = (usize)((ptr - DEFAULT_SIZE_PREFIX) - current_page.memory);
+		current_page.used = (usz)((ptr - DEFAULT_SIZE_PREFIX) - current_page.memory);
 	}
 	current_page.last_ptr = null;
 }
@@ -32,26 +32,26 @@ private fn void DynamicArenaAllocator.free(DynamicArenaAllocator* this, void* pt
  * @require old_pointer && size > 0
  * @require this.page `tried to realloc pointer on invalid allocator`
  */
-private fn void*! DynamicArenaAllocator._realloc(DynamicArenaAllocator* this, void* old_pointer, usize size, usize alignment, usize offset)
+private fn void*! DynamicArenaAllocator._realloc(DynamicArenaAllocator* this, void* old_pointer, usz size, usz alignment, usz offset)
 {
 	DynamicArenaPage* current_page = this.page;
 	alignment = alignment_for_allocation(alignment);
-	usize* old_size_ptr = old_pointer - DEFAULT_SIZE_PREFIX;
-	usize old_size = *old_size_ptr;
+	usz* old_size_ptr = old_pointer - DEFAULT_SIZE_PREFIX;
+	usz old_size = *old_size_ptr;
 	// We have the old pointer and it's correctly aligned.
 	if (old_size >= size && mem::ptr_is_aligned(old_pointer, alignment))
 	{
 		*old_size_ptr = size;
 		if (current_page.last_ptr == old_pointer)
 		{
-			current_page.used = (usize)((old_pointer - DEFAULT_SIZE_PREFIX) - current_page.memory);
+			current_page.used = (usz)((old_pointer - DEFAULT_SIZE_PREFIX) - current_page.memory);
 		}
 		return old_pointer;
 	}
 	if REUSE: (current_page.last_ptr == old_pointer && mem::ptr_is_aligned(old_pointer, alignment))
 	{
 		assert(size > old_size);
-		usize add_size = size - old_size;
+		usz add_size = size - old_size;
 		if (add_size + current_page.used > current_page.total) break REUSE;
 		*old_size_ptr = size;
 		current_page.used += add_size;
@@ -82,10 +82,10 @@ private fn void DynamicArenaAllocator.reset(DynamicArenaAllocator* this)
  * @require math::is_power_of_2(alignment)
  * @require size > 0
  */
-private fn void*! DynamicArenaAllocator._alloc_new(DynamicArenaAllocator* this, usize size, usize alignment, usize offset)
+private fn void*! DynamicArenaAllocator._alloc_new(DynamicArenaAllocator* this, usz size, usz alignment, usz offset)
 {
 	// First, make sure that we can align it, extending the page size if needed.
-	usize page_size = max(this.page_size, mem::aligned_offset(size + DynamicArenaChunk.sizeof + offset, alignment) - offset);
+	usz page_size = max(this.page_size, mem::aligned_offset(size + DynamicArenaChunk.sizeof + offset, alignment) - offset);
 
 	// Grab the page without alignment (we do it ourselves)
 	void* mem = this.backing_allocator.alloc(page_size)?;
@@ -113,7 +113,7 @@ private fn void*! DynamicArenaAllocator._alloc_new(DynamicArenaAllocator* this,
  * @require size > 0
  * @require this
  */
-private fn void*! DynamicArenaAllocator._alloc(DynamicArenaAllocator* this, usize size, usize alignment, usize offset)
+private fn void*! DynamicArenaAllocator._alloc(DynamicArenaAllocator* this, usz size, usz alignment, usz offset)
 {
 	alignment = alignment_for_allocation(alignment);
 	DynamicArenaPage* page = this.page;
@@ -125,7 +125,7 @@ private fn void*! DynamicArenaAllocator._alloc(DynamicArenaAllocator* this, usiz
 	}
     if (!page) return this._alloc_new(size, alignment, offset);
     void* start = mem::aligned_pointer(page.memory + page.used + DynamicArenaChunk.sizeof + offset, alignment) - offset;
-    usize new_used = start - page.memory + size;
+    usz new_used = start - page.memory + size;
     if ALLOCATE_NEW: (new_used > page.total)
     {
         if ((page = this.unused_page))
@@ -155,7 +155,7 @@ private fn void*! DynamicArenaAllocator._alloc(DynamicArenaAllocator* this, usiz
  * @require !alignment || math::is_power_of_2(alignment)
  * @require data `unexpectedly missing the allocator`
  */
-private fn void*! dynamic_arena_allocator_function(Allocator* data, usize size, usize alignment, usize offset, void* old_pointer, AllocationKind kind)
+private fn void*! dynamic_arena_allocator_function(Allocator* data, usz size, usz alignment, usz offset, void* old_pointer, AllocationKind kind)
 {
 	DynamicArenaAllocator* allocator = (DynamicArenaAllocator*)data;
 	switch (kind)
diff --git a/lib/std/core/allocators/mem_allocator_fn.c3 b/lib/std/core/allocators/mem_allocator_fn.c3
index 2fb46d31d..52830af81 100644
--- a/lib/std/core/allocators/mem_allocator_fn.c3
+++ b/lib/std/core/allocators/mem_allocator_fn.c3
@@ -4,7 +4,7 @@ import libc;
 private const Allocator _NULL_ALLOCATOR = { &null_allocator_fn };
 private const Allocator _SYSTEM_ALLOCATOR = { &libc_allocator_fn };
 
-private fn void*! null_allocator_fn(Allocator* this, usize bytes, usize alignment, usize offset, void* old_pointer, AllocationKind kind)
+private fn void*! null_allocator_fn(Allocator* this, usz bytes, usz alignment, usz offset, void* old_pointer, AllocationKind kind)
 {
 	switch (kind)
 	{
@@ -22,7 +22,7 @@ private fn void*! null_allocator_fn(Allocator* this, usize bytes, usize alignmen
 
 private struct AlignedBlock
 {
-	usize len;
+	usz len;
 	void* start;
 }
 
@@ -31,9 +31,9 @@ private struct AlignedBlock
  * @require bytes > 0
  * @require alignment > 0
  **/
-private fn void* _libc_aligned_alloc(usize bytes, usize alignment, usize offset) @inline
+private fn void* _libc_aligned_alloc(usz bytes, usz alignment, usz offset) @inline
 {
-	usize header = mem::aligned_offset(AlignedBlock.sizeof + offset, alignment) - offset;
+	usz header = mem::aligned_offset(AlignedBlock.sizeof + offset, alignment) - offset;
 	void* data = libc::malloc(header + bytes);
     void* mem = mem::aligned_pointer(data + offset, alignment) - offset;
 	assert(mem > data);
@@ -46,9 +46,9 @@ private fn void* _libc_aligned_alloc(usize bytes, usize alignment, usize offset)
  * @require bytes > 0
  * @require alignment > 0
  **/
-private fn void* _libc_aligned_calloc(usize bytes, usize alignment, usize offset) @inline
+private fn void* _libc_aligned_calloc(usz bytes, usz alignment, usz offset) @inline
 {
-	usize header = mem::aligned_offset(AlignedBlock.sizeof + offset, alignment) - offset;
+	usz header = mem::aligned_offset(AlignedBlock.sizeof + offset, alignment) - offset;
 	void* data = libc::calloc(header + bytes, 1);
 	void* mem = mem::aligned_pointer(data + offset, alignment) - offset;
 	AlignedBlock* desc = (AlignedBlock*)mem - 1;
@@ -61,7 +61,7 @@ private fn void* _libc_aligned_calloc(usize bytes, usize alignment, usize offset
  * @require bytes > 0
  * @require alignment > 0
  **/
-private fn void* _libc_aligned_realloc(void* old_pointer, usize bytes, usize alignment, usize offset) @inline
+private fn void* _libc_aligned_realloc(void* old_pointer, usz bytes, usz alignment, usz offset) @inline
 {
 	AlignedBlock* desc = (AlignedBlock*)old_pointer - 1;
     void* data_start = desc.start;
@@ -77,7 +77,7 @@ private fn void _libc_aligned_free(void* old_pointer) @inline
 	libc::free(desc.start);
 }
 
-fn void*! libc_allocator_fn(Allocator* unused, usize bytes, usize alignment, usize offset, void* old_pointer, AllocationKind kind) @inline
+fn void*! libc_allocator_fn(Allocator* unused, usz bytes, usz alignment, usz offset, void* old_pointer, AllocationKind kind) @inline
 {
 	if (!alignment) alignment = DEFAULT_MEM_ALIGNMENT;
 	assert(math::is_power_of_2(alignment), "Alignment was not a power of 2");
diff --git a/lib/std/core/allocators/temp_allocator.c3 b/lib/std/core/allocators/temp_allocator.c3
index cd5edfcc8..bb7a863a2 100644
--- a/lib/std/core/allocators/temp_allocator.c3
+++ b/lib/std/core/allocators/temp_allocator.c3
@@ -3,7 +3,7 @@ import std::io;
 
 private struct TempAllocatorChunk
 {
-	usize size;
+	usz size;
 	char[*] data;
 }
 
@@ -12,32 +12,32 @@ struct TempAllocator
 	inline Allocator allocator;
 	Allocator* backing_allocator;
 	TempAllocatorPage* last_page;
-	usize used;
-	usize capacity;
+	usz used;
+	usz capacity;
 	char[*] data;
 }
 
 
-private const usize PAGE_IS_ALIGNED = (usize)isize.max + 1;
+private const usz PAGE_IS_ALIGNED = (usz)isz.max + 1;
 
 
 struct TempAllocatorPage
 {
 	TempAllocatorPage* prev_page;
 	void* start;
-	usize mark;
-	usize size;
-	usize ident;
+	usz mark;
+	usz size;
+	usz ident;
 	char[*] data;
 }
 
-macro usize TempAllocatorPage.pagesize(TempAllocatorPage* page) { return page.size & ~PAGE_IS_ALIGNED; }
+macro usz TempAllocatorPage.pagesize(TempAllocatorPage* page) { return page.size & ~PAGE_IS_ALIGNED; }
 macro bool TempAllocatorPage.is_aligned(TempAllocatorPage* page) { return page.size & PAGE_IS_ALIGNED == PAGE_IS_ALIGNED; }
 
 /**
  * @require size >= 16
  **/
-fn TempAllocator*! new_temp(usize size, Allocator* backing_allocator)
+fn TempAllocator*! new_temp(usz size, Allocator* backing_allocator)
 {
 	TempAllocator* allocator = backing_allocator.alloc(size + TempAllocator.sizeof)?;
 	allocator.last_page = null;
@@ -52,7 +52,7 @@ fn TempAllocator*! new_temp(usize size, Allocator* backing_allocator)
  * @require !alignment || math::is_power_of_2(alignment)
  * @require data `unexpectedly missing the allocator`
  */
-private fn void*! temp_allocator_function(Allocator* data, usize size, usize alignment, usize offset, void* old_pointer, AllocationKind kind)
+private fn void*! temp_allocator_function(Allocator* data, usz size, usz alignment, usz offset, void* old_pointer, AllocationKind kind)
 {
 	TempAllocator* arena = (TempAllocator*)data;
 	switch (kind)
@@ -92,13 +92,13 @@ private fn void! TempAllocator._free(TempAllocator* this, void* old_pointer)
 
 	// TODO fix free
 	assert((uptr)old_pointer >= (uptr)&this.data, "Pointer originates from a different allocator.");
-	usize old_size = *(usize*)(old_pointer - DEFAULT_SIZE_PREFIX);
+	usz old_size = *(usz*)(old_pointer - DEFAULT_SIZE_PREFIX);
 	if (old_pointer + old_size == &this.data[this.used])
     {
         this.used -= old_size;
     }
 }
-private fn void! TempAllocator._reset(TempAllocator* this, usize mark)
+private fn void! TempAllocator._reset(TempAllocator* this, usz mark)
 {
 	TempAllocatorPage *last_page = this.last_page;
 	while (last_page && last_page.mark > mark)
@@ -118,7 +118,7 @@ private fn void! TempAllocator._free_page(TempAllocator* this, TempAllocatorPage
 	return this.backing_allocator.free(mem);
 }
 
-private fn void*! TempAllocator._realloc_page(TempAllocator* this, TempAllocatorPage* page, usize size, usize alignment, usize offset) @inline
+private fn void*! TempAllocator._realloc_page(TempAllocator* this, TempAllocatorPage* page, usz size, usz alignment, usz offset) @inline
 {
 	// Then the actual start pointer:
 	void* real_pointer = page.start;
@@ -131,7 +131,7 @@ private fn void*! TempAllocator._realloc_page(TempAllocator* this, TempAllocator
 		pointer_to_prev = &((*pointer_to_prev).prev_page);
 	}
 	*pointer_to_prev = page.prev_page;
-	usize page_size = page.pagesize();
+	usz page_size = page.pagesize();
 	// Clear on size > original size.
 	void* data = this._alloc(size, alignment, offset, false)?;
 	mem::copy(data, &page.data[0], page_size, DEFAULT_MEM_ALIGNMENT, DEFAULT_MEM_ALIGNMENT);
@@ -146,10 +146,10 @@ private fn void*! TempAllocator._realloc_page(TempAllocator* this, TempAllocator
 	return data;
 }
 
-private fn void*! TempAllocator._realloc(TempAllocator* this, void* pointer, usize size, usize alignment, usize offset) @inline
+private fn void*! TempAllocator._realloc(TempAllocator* this, void* pointer, usz size, usz alignment, usz offset) @inline
 {
 	TempAllocatorChunk *chunk = pointer - TempAllocatorChunk.sizeof;
-	if (chunk.size == (usize)-1)
+	if (chunk.size == (usz)-1)
 	{
 		assert(this.last_page, "Realloc of non temp pointer");
 		// First grab the page
@@ -172,7 +172,7 @@ private fn void*! TempAllocator._realloc(TempAllocator* this, void* pointer, usi
  * @require alignment <= MAX_MEMORY_ALIGNMENT `alignment too big`
  * @require this != null
  **/
-private fn void*! TempAllocator._alloc(TempAllocator* this, usize size, usize alignment, usize offset, bool clear)
+private fn void*! TempAllocator._alloc(TempAllocator* this, usz size, usz alignment, usz offset, bool clear)
 {
 	void* start_mem = &this.data;
 	void* starting_ptr = start_mem + this.used;
@@ -182,7 +182,7 @@ private fn void*! TempAllocator._alloc(TempAllocator* this, usize size, usize al
 	{
 		mem = mem::aligned_pointer(mem + offset, alignment) - offset;
 	}
-	usize new_usage = (usize)(mem - start_mem) + size;
+	usz new_usage = (usz)(mem - start_mem) + size;
 
 	// Arena alignment, simple!
 	if (new_usage <= this.capacity)
@@ -201,7 +201,7 @@ private fn void*! TempAllocator._alloc(TempAllocator* this, usize size, usize al
 	if (alignment > DEFAULT_MEM_ALIGNMENT || offset)
 	{
 		// This is actually simpler, since it will create the offset for us.
-		usize total_alloc_size = TempAllocatorPage.sizeof + size;
+		usz total_alloc_size = TempAllocatorPage.sizeof + size;
     	if (clear)
 		{
 			page = this.backing_allocator.calloc_aligned(total_alloc_size, alignment, TempAllocatorPage.sizeof + offset)?;
@@ -216,8 +216,8 @@ private fn void*! TempAllocator._alloc(TempAllocator* this, usize size, usize al
 	else
 	{
 		// Here we might need to pad
-		usize padded_header_size = mem::aligned_offset(TempAllocatorPage.sizeof, DEFAULT_MEM_ALIGNMENT);
-		usize total_alloc_size = padded_header_size + size;
+		usz padded_header_size = mem::aligned_offset(TempAllocatorPage.sizeof, DEFAULT_MEM_ALIGNMENT);
+		usz total_alloc_size = padded_header_size + size;
 		void* alloc = (clear ? this.backing_allocator.calloc(total_alloc_size) : this.backing_allocator.alloc(total_alloc_size))?;
 
 		// Find the page.
@@ -229,7 +229,7 @@ private fn void*! TempAllocator._alloc(TempAllocator* this, usize size, usize al
 	}
 
 	// Mark it as a page
-	page.ident = ~(usize)0;
+	page.ident = ~(usz)0;
 	// Store when it was created
 	page.mark = ++this.used;
 	// Hook up the page.
diff --git a/lib/std/core/builtin.c3 b/lib/std/core/builtin.c3
index a603813cc..5ce0c42e0 100644
--- a/lib/std/core/builtin.c3
+++ b/lib/std/core/builtin.c3
@@ -95,7 +95,7 @@ macro void unreachable($string = "Unreachable statement reached.") @builtin @nor
 
 macro bitcast(expr, $Type) @builtin
 {
-    var $size = (usize)($sizeof(expr));
+    var $size = (usz)($sizeof(expr));
     $assert($size == $Type.sizeof, "Cannot bitcast between types of different size.");
     $Type x = void;
     mem::copy(&x, &expr, $size, $Type.alignof, $alignof(expr));
diff --git a/lib/std/core/conv.c3 b/lib/std/core/conv.c3
index 203e17283..2cab52169 100644
--- a/lib/std/core/conv.c3
+++ b/lib/std/core/conv.c3
@@ -14,7 +14,7 @@ private const uint UTF16_SURROGATE_HIGH_VALUE = 0xD800;
  * @param [out] output `the resulting buffer`
  * @param available `the size available`
  **/
-fn usize! char32_to_utf8(Char32 c, char* output, usize available)
+fn usz! char32_to_utf8(Char32 c, char* output, usz available)
 {
 	if (!available) return UnicodeResult.CONVERSION_FAILED!;
 	switch (true)
@@ -71,7 +71,7 @@ fn void char32_to_utf16_unsafe(Char32 c, Char16** output)
  * @param [inout] available `amount of UTF16 data available.`
  * @param [inout] output `the resulting utf8 buffer to write to.`
  **/
-fn void! char16_to_utf8_unsafe(Char16 *ptr, usize *available, char** output)
+fn void! char16_to_utf8_unsafe(Char16 *ptr, usz *available, char** output)
 {
 	Char16 high = *ptr;
 	if (high & UTF16_SURROGATE_GENERIC_MASK != UTF16_SURROGATE_GENERIC_VALUE)
@@ -128,9 +128,9 @@ fn void char32_to_utf8_unsafe(Char32 c, char** output)
  * @param [inout] size `Set to max characters to read, set to characters read`
  * @return `the parsed 32 bit codepoint`
  **/
-fn Char32! utf8_to_char32(char* ptr, usize* size)
+fn Char32! utf8_to_char32(char* ptr, usz* size)
 {
-	usize max_size = *size;
+	usz max_size = *size;
 	if (max_size < 1) return UnicodeResult.INVALID_UTF8!;
 	char c = (ptr++)[0];
 
@@ -178,9 +178,9 @@ fn Char32! utf8_to_char32(char* ptr, usize* size)
  * @param utf8 `An UTF-8 encoded slice of bytes`
  * @return `the number of encoded code points`
  **/
-fn usize utf8_codepoints(char[] utf8)
+fn usz utf8_codepoints(char[] utf8)
 {
-	usize len = 0;
+	usz len = 0;
 	foreach (char c : utf8)
 	{
 		if (c & 0xC0 != 0x80) len++;
@@ -193,9 +193,9 @@ fn usize utf8_codepoints(char[] utf8)
  * @param [in] utf32 `the utf32 data to calculate from`
  * @return `the length of the resulting UTF8 array`
  **/
-fn usize utf8len_for_utf32(Char32[] utf32)
+fn usz utf8len_for_utf32(Char32[] utf32)
 {
-	usize len = 0;
+	usz len = 0;
 	foreach (Char32 uc : utf32)
 	{
 		switch (true)
@@ -218,11 +218,11 @@ fn usize utf8len_for_utf32(Char32[] utf32)
  * @param [in] utf16 `the utf16 data to calculate from`
  * @return `the length of the resulting UTF8 array`
  **/
-fn usize utf8len_for_utf16(Char16[] utf16)
+fn usz utf8len_for_utf16(Char16[] utf16)
 {
-	usize len = 0;
-	usize len16 = utf16.len;
-	for (usize i = 0; i < len16; i++)
+	usz len = 0;
+	usz len16 = utf16.len;
+	for (usz i = 0; i < len16; i++)
 	{
 		Char16 c = utf16[i];
 		if (c & UTF16_SURROGATE_GENERIC_MASK != UTF16_SURROGATE_GENERIC_VALUE)
@@ -250,11 +250,11 @@ fn usize utf8len_for_utf16(Char16[] utf16)
  * @param utf8 `the utf8 data to calculate from`
  * @return `the length of the resulting UTF16 array`
  **/
-fn usize utf16len_for_utf8(char[] utf8)
+fn usz utf16len_for_utf8(char[] utf8)
 {
-	usize len = utf8.len;
-	usize len16 = 0;
-	for (usize i = 0; i < len; i++)
+	usz len = utf8.len;
+	usz len16 = 0;
+	for (usz i = 0; i < len; i++)
 	{
 		len16++;
 		char c = utf8[i];
@@ -273,9 +273,9 @@ fn usize utf16len_for_utf8(char[] utf8)
  * @param [in] utf32 `the UTF32 array to check the length for`
  * @return `the required length of an UTF16 array to hold the UTF32 data.`
  **/
-fn usize utf16len_for_utf32(Char32[] utf32)
+fn usz utf16len_for_utf32(Char32[] utf32)
 {
-	usize len = utf32.len;
+	usz len = utf32.len;
 	foreach (Char32 uc : utf32)
 	{
 		if (uc >= UTF16_SURROGATE_OFFSET) len++;
@@ -290,13 +290,13 @@ fn usize utf16len_for_utf32(Char32[] utf32)
  * @param [out] utf8_buffer
  * @return `the number of bytes written.`
  **/
-fn usize! utf32to8(Char32[] utf32, char[] utf8_buffer)
+fn usz! utf32to8(Char32[] utf32, char[] utf8_buffer)
 {
-	usize len = utf8_buffer.len;
+	usz len = utf8_buffer.len;
 	char* ptr = utf8_buffer.ptr;
 	foreach (Char32 uc : utf32)
 	{
-		usize used = char32_to_utf8(uc, ptr, len) @inline?;
+		usz used = char32_to_utf8(uc, ptr, len) @inline?;
 		len -= used;
 		ptr += used;
 	}
@@ -310,16 +310,16 @@ fn usize! utf32to8(Char32[] utf32, char[] utf8_buffer)
  * @param [out] utf32_buffer
  * @return `the number of Char32s written.`
  **/
-fn usize! utf8to32(char[] utf8, Char32[] utf32_buffer)
+fn usz! utf8to32(char[] utf8, Char32[] utf32_buffer)
 {
-	usize len = utf8.len;
+	usz len = utf8.len;
 	Char32* ptr = utf32_buffer.ptr;
-    usize len32 = 0;
-    usize buf_len = utf32_buffer.len;
-    for (usize i = 0; i < len;)
+    usz len32 = 0;
+    usz buf_len = utf32_buffer.len;
+    for (usz i = 0; i < len;)
     {
         if (len32 == buf_len) return UnicodeResult.CONVERSION_FAILED!;
-        usize width = len - i;
+        usz width = len - i;
     	Char32 uc = utf8_to_char32(&utf8[i], &width) @inline?;
     	i += width;
     	ptr[len32++] = uc;
@@ -337,10 +337,10 @@ fn usize! utf8to32(char[] utf8, Char32[] utf32_buffer)
  **/
 fn void! utf16to8_unsafe(Char16[] utf16, char* utf8_buffer)
 {
-	usize len16 = utf16.len;
-	for (usize i = 0; i < len16;)
+	usz len16 = utf16.len;
+	for (usz i = 0; i < len16;)
 	{
-		usize available = len16 - i;
+		usz available = len16 - i;
 		char16_to_utf8_unsafe(&utf16[i], &available, &utf8_buffer) @inline?;
 		i += available;
 	}
@@ -356,10 +356,10 @@ fn void! utf16to8_unsafe(Char16[] utf16, char* utf8_buffer)
  **/
 fn void! utf8to32_unsafe(char[] utf8, Char32* utf32_buffer)
 {
-	usize len = utf8.len;
-	for (usize i = 0; i < len;)
+	usz len = utf8.len;
+	for (usz i = 0; i < len;)
     {
-        usize width = len - i;
+        usz width = len - i;
     	Char32 uc = utf8_to_char32(&utf8[i], &width) @inline?;
     	i += width;
     	(utf32_buffer++)[0] = uc;
@@ -376,10 +376,10 @@ fn void! utf8to32_unsafe(char[] utf8, Char32* utf32_buffer)
  **/
 fn void! utf8to16_unsafe(char[] utf8, Char16* utf16_buffer)
 {
-	usize len = utf8.len;
-    for (usize i = 0; i < len;)
+	usz len = utf8.len;
+    for (usz i = 0; i < len;)
     {
-        usize width = len - i;
+        usz width = len - i;
     	Char32 uc = utf8_to_char32(&utf8[i], &width) @inline?;
         char32_to_utf16_unsafe(uc, &utf16_buffer) @inline;
         i += width;
diff --git a/lib/std/core/env.c3 b/lib/std/core/env.c3
index 9bfca0580..e8c38c4e4 100644
--- a/lib/std/core/env.c3
+++ b/lib/std/core/env.c3
@@ -59,4 +59,4 @@ const bool I128_SUPPORT = $$PLATFORM_I128_SUPPORTED;
 const bool F128_SUPPORT = $$PLATFORM_F128_SUPPORTED;
 const bool F16_SUPPORT = $$PLATFORM_F16_SUPPORTED;
 const bool COMPILER_SAFE_MODE = $$COMPILER_SAFE_MODE;
-const usize TEMP_ALLOCATOR_SIZE = 128 * 1024;
\ No newline at end of file
+const usz TEMP_ALLOCATOR_SIZE = 128 * 1024;
\ No newline at end of file
diff --git a/lib/std/core/mem.c3 b/lib/std/core/mem.c3
index 00a444a5a..96e46d71a 100644
--- a/lib/std/core/mem.c3
+++ b/lib/std/core/mem.c3
@@ -16,12 +16,12 @@ macro @volatile_store(&x, y)
 /**
  * @require math::is_power_of_2(alignment)
  **/
-fn usize aligned_offset(usize offset, usize alignment)
+fn usz aligned_offset(usz offset, usz alignment)
 {
 	return alignment * ((offset + alignment - 1) / alignment);
 }
 
-macro void* aligned_pointer(void* ptr, usize alignment)
+macro void* aligned_pointer(void* ptr, usz alignment)
 {
 	return (void*)(uptr)aligned_offset((uptr)ptr, alignment);
 }
@@ -30,27 +30,27 @@ macro void* aligned_pointer(void* ptr, usize alignment)
 /**
  * @require math::is_power_of_2(alignment)
  **/
-fn bool ptr_is_aligned(void* ptr, usize alignment) @inline
+fn bool ptr_is_aligned(void* ptr, usz alignment) @inline
 {
 	return (uptr)ptr & ((uptr)alignment - 1) == 0;
 }
 
-macro void copy(void* dst, void* src, usize len, usize $dst_align = 0, usize $src_align = 0, bool $is_volatile = false)
+macro void copy(void* dst, void* src, usz len, usz $dst_align = 0, usz $src_align = 0, bool $is_volatile = false)
 {
 	$$memcpy(dst, src, len, $is_volatile, $dst_align, $src_align);
 }
 
-macro void set(void* dst, char val, usize len, usize $dst_align = 0, bool $is_volatile = false)
+macro void set(void* dst, char val, usz len, usz $dst_align = 0, bool $is_volatile = false)
 {
 	$$memset(dst, val, len, $is_volatile, $dst_align);
 }
 
-macro void move(void* dst, void* src, usize len, usize $dst_align = 0, usize $src_align = 0, bool $is_volatile = false)
+macro void move(void* dst, void* src, usz len, usz $dst_align = 0, usz $src_align = 0, bool $is_volatile = false)
 {
 	$$memmove(dst, src, len, $is_volatile, $dst_align, $src_align);
 }
 
-macro void clear(void* dst, usize len, usize $dst_align = 0, bool $is_volatile = false)
+macro void clear(void* dst, usz len, usz $dst_align = 0, bool $is_volatile = false)
 {
 	$$memset(dst, (char)0, len, $is_volatile, $dst_align);
 }
@@ -62,7 +62,7 @@ macro void clear(void* dst, usize len, usize $dst_align = 0, bool $is_volatile =
  * @require $typeof(a).kindof != TypeKind.POINTER || len > -1
  * @checked (a = b), (b = a)
  **/
-macro bool equals(a, b, isize len = -1, usize $align = 0)
+macro bool equals(a, b, isz len = -1, usz $align = 0)
 {
 	$if (!$align):
 		$align = $typeof(a[0]).alignof;
@@ -93,13 +93,13 @@ macro bool equals(a, b, isize len = -1, usize $align = 0)
 			var $Type = ulong;
 	$endswitch;
 	var $step = $Type.sizeof;
-	usize end = len / $step;
-	for (usize i = 0; i < end; i++)
+	usz end = len / $step;
+	for (usz i = 0; i < end; i++)
 	{
 		if ((($Type*)x)[i] != (($Type*)y)[i]) return false;
 	}
-	usize last = len % $align;
-	for (usize i = len - last; i < len; i++)
+	usz last = len % $align;
+	for (usz i = len - last; i < len; i++)
 	{
 		if (((char*)x)[i] != ((char*)y)[i]) return false;
 	}
@@ -120,12 +120,12 @@ macro @tclone(&value) @builtin
 	return x;
 }
 
-fn void* malloc(usize size) @builtin @inline
+fn void* malloc(usz size) @builtin @inline
 {
 	return thread_allocator.alloc(size)!!;
 }
 
-fn void*! malloc_checked(usize size) @builtin @inline
+fn void*! malloc_checked(usz size) @builtin @inline
 {
 	return thread_allocator.alloc(size);
 }
@@ -133,12 +133,12 @@ fn void*! malloc_checked(usize size) @builtin @inline
 /**
  * @require alignment && math::is_power_of_2(alignment)
  */
-fn void*! malloc_aligned(usize size, usize alignment) @builtin @inline
+fn void*! malloc_aligned(usz size, usz alignment) @builtin @inline
 {
 	return thread_allocator.alloc_aligned(size, alignment);
 }
 
-fn char[] alloc_bytes(usize bytes) @inline
+fn char[] alloc_bytes(usz bytes) @inline
 {
 	return ((char*)thread_allocator.alloc(bytes))[:bytes]!!;
 }
@@ -149,12 +149,12 @@ macro alloc($Type)
 }
 
 
-fn void* calloc(usize size) @builtin @inline
+fn void* calloc(usz size) @builtin @inline
 {
 	return thread_allocator.calloc(size)!!;
 }
 
-fn void*! calloc_checked(usize size) @builtin @inline
+fn void*! calloc_checked(usz size) @builtin @inline
 {
 	return thread_allocator.calloc(size);
 }
@@ -162,17 +162,17 @@ fn void*! calloc_checked(usize size) @builtin @inline
 /**
  * @require alignment && math::is_power_of_2(alignment)
  */
-fn void*! calloc_aligned(usize size, usize alignment) @builtin @inline
+fn void*! calloc_aligned(usz size, usz alignment) @builtin @inline
 {
 	return thread_allocator.calloc_aligned(size, alignment);
 }
 
-fn void* realloc(void *ptr, usize new_size) @builtin @inline
+fn void* realloc(void *ptr, usz new_size) @builtin @inline
 {
 	return thread_allocator.realloc(ptr, new_size)!!;
 }
 
-fn void*! realloc_checked(void *ptr, usize new_size) @builtin @inline
+fn void*! realloc_checked(void *ptr, usz new_size) @builtin @inline
 {
 	return thread_allocator.realloc(ptr, new_size);
 }
@@ -180,7 +180,7 @@ fn void*! realloc_checked(void *ptr, usize new_size) @builtin @inline
 /**
  * @require alignment && math::is_power_of_2(alignment)
  */
-fn void*! realloc_aligned(void *ptr, usize new_size, usize alignment) @builtin @inline
+fn void*! realloc_aligned(void *ptr, usz new_size, usz alignment) @builtin @inline
 {
 	return thread_allocator.realloc_aligned(ptr, new_size, alignment);
 }
@@ -210,7 +210,7 @@ macro void @tscoped(;@body())
 {
 	Allocator* old_allocator = thread_allocator;
 	TempAllocator* temp = temp_allocator();
-	usize mark = temp.mark()!!;
+	usz mark = temp.mark()!!;
 	thread_allocator = temp;
 	defer temp.reset(mark);
 	defer thread_allocator = old_allocator;
@@ -222,17 +222,17 @@ macro talloc($Type) @builtin
 	return temp_allocator().alloc_aligned($Type.sizeof, $Type.alignof)!!;
 }
 
-fn void* tmalloc(usize size, usize alignment = allocator::DEFAULT_MEM_ALIGNMENT) @builtin @inline
+fn void* tmalloc(usz size, usz alignment = allocator::DEFAULT_MEM_ALIGNMENT) @builtin @inline
 {
     return temp_allocator().alloc_aligned(size, alignment)!!;
 }
 
-fn void* tcalloc(usize size, usize alignment = allocator::DEFAULT_MEM_ALIGNMENT) @builtin @inline
+fn void* tcalloc(usz size, usz alignment = allocator::DEFAULT_MEM_ALIGNMENT) @builtin @inline
 {
 	return temp_allocator().calloc_aligned(size, alignment)!!;
 }
 
-fn void* trealloc(void* ptr, usize size, usize alignment = allocator::DEFAULT_MEM_ALIGNMENT) @builtin @inline
+fn void* trealloc(void* ptr, usz size, usz alignment = allocator::DEFAULT_MEM_ALIGNMENT) @builtin @inline
 {
 	return temp_allocator().realloc_aligned(ptr, size, alignment)!!;
 }
@@ -240,7 +240,7 @@ fn void* trealloc(void* ptr, usize size, usize alignment = allocator::DEFAULT_ME
 macro void @pool(;@body) @builtin
 {
 	TempAllocator* temp = temp_allocator();
-	usize mark = temp.used;
+	usz mark = temp.used;
 	defer temp.reset(mark);
 	@body();
 }
diff --git a/lib/std/core/mem_allocator.c3 b/lib/std/core/mem_allocator.c3
index c52e173e1..2cb10d16b 100644
--- a/lib/std/core/mem_allocator.c3
+++ b/lib/std/core/mem_allocator.c3
@@ -2,13 +2,13 @@ module std::core::mem::allocator;
 
 const MAX_MEMORY_ALIGNMENT = 0x1000_0000;
 const DEFAULT_MEM_ALIGNMENT = (void*.alignof) * 2;
-const DEFAULT_SIZE_PREFIX = usize.sizeof;
-const DEFAULT_SIZE_PREFIX_ALIGNMENT = usize.alignof;
+const DEFAULT_SIZE_PREFIX = usz.sizeof;
+const DEFAULT_SIZE_PREFIX_ALIGNMENT = usz.alignof;
 
 const Allocator* NULL_ALLOCATOR = &_NULL_ALLOCATOR;
 const Allocator* LIBC_ALLOCATOR = &_SYSTEM_ALLOCATOR;
 
-define AllocatorFunction = fn void*!(Allocator* allocator, usize new_size, usize alignment, usize offset, void* old_pointer, AllocationKind kind);
+define AllocatorFunction = fn void*!(Allocator* allocator, usz new_size, usz alignment, usz offset, void* old_pointer, AllocationKind kind);
 
 struct Allocator
 {
@@ -38,7 +38,7 @@ fault AllocationFailure
 
 
 
-fn void*! Allocator.alloc(Allocator* allocator, usize size) @inline
+fn void*! Allocator.alloc(Allocator* allocator, usz size) @inline
 {
 	return allocator.function(allocator, size, 0, 0, null, ALLOC);
 }
@@ -46,12 +46,12 @@ fn void*! Allocator.alloc(Allocator* allocator, usize size) @inline
 /**
  * @require alignment && math::is_power_of_2(alignment)
  */
-fn void*! Allocator.alloc_aligned(Allocator* allocator, usize size, usize alignment, usize offset = 0) @inline
+fn void*! Allocator.alloc_aligned(Allocator* allocator, usz size, usz alignment, usz offset = 0) @inline
 {
 	return allocator.function(allocator, size, alignment, offset, null, ALIGNED_ALLOC);
 }
 
-fn void*! Allocator.realloc(Allocator* allocator, void* old_pointer, usize size) @inline
+fn void*! Allocator.realloc(Allocator* allocator, void* old_pointer, usz size) @inline
 {
 	return allocator.function(allocator, size, 0, 0, old_pointer, REALLOC);
 }
@@ -59,18 +59,18 @@ fn void*! Allocator.realloc(Allocator* allocator, void* old_pointer, usize size)
 /**
  * @require alignment && math::is_power_of_2(alignment)
  */
-fn void*! Allocator.realloc_aligned(Allocator* allocator, void* old_pointer, usize size, usize alignment, usize offset = 0) @inline
+fn void*! Allocator.realloc_aligned(Allocator* allocator, void* old_pointer, usz size, usz alignment, usz offset = 0) @inline
 {
 	return allocator.function(allocator, size, alignment, offset, old_pointer, ALIGNED_REALLOC);
 }
 
-fn usize! Allocator.mark(Allocator* allocator) @inline
+fn usz! Allocator.mark(Allocator* allocator) @inline
 {
-	return (usize)(uptr)allocator.function(allocator, 0, 0, 0, null, MARK);
+	return (usz)(uptr)allocator.function(allocator, 0, 0, 0, null, MARK);
 }
 
 
-fn void*! Allocator.calloc(Allocator* allocator, usize size) @inline
+fn void*! Allocator.calloc(Allocator* allocator, usz size) @inline
 {
 	return allocator.function(allocator, size, 0, 0, null, CALLOC);
 }
@@ -78,7 +78,7 @@ fn void*! Allocator.calloc(Allocator* allocator, usize size) @inline
 /**
  * @require alignment && math::is_power_of_2(alignment)
  */
-fn void*! Allocator.calloc_aligned(Allocator* allocator, usize size, usize alignment, usize offset = 0) @inline
+fn void*! Allocator.calloc_aligned(Allocator* allocator, usz size, usz alignment, usz offset = 0) @inline
 {
 	return allocator.function(allocator, size, alignment, offset, null, ALIGNED_CALLOC);
 }
@@ -93,12 +93,12 @@ fn void! Allocator.free_aligned(Allocator* allocator, void* old_pointer) @inline
 	allocator.function(allocator, 0, 0, 0, old_pointer, ALIGNED_FREE)?;
 }
 
-fn void Allocator.reset(Allocator* allocator, usize mark = 0)
+fn void Allocator.reset(Allocator* allocator, usz mark = 0)
 {
 	allocator.function(allocator, mark, 0, 0, null, RESET)!!;
 }
 
-private fn usize alignment_for_allocation(usize alignment) @inline
+private fn usz alignment_for_allocation(usz alignment) @inline
 {
 	if (alignment < DEFAULT_MEM_ALIGNMENT)
 	{
@@ -113,14 +113,14 @@ struct DynamicArenaAllocator
 	Allocator* backing_allocator;
 	DynamicArenaPage* page;
 	DynamicArenaPage* unused_page;
-	usize page_size;
+	usz page_size;
 }
 
 /**
  * @require page_size >= 128
  * @require this != null
  **/
-fn void DynamicArenaAllocator.init(DynamicArenaAllocator* this, usize page_size, Allocator* backing_allocator = mem::current_allocator())
+fn void DynamicArenaAllocator.init(DynamicArenaAllocator* this, usz page_size, Allocator* backing_allocator = mem::current_allocator())
 {
 	this.function = &dynamic_arena_allocator_function;
 	this.page = null;
@@ -157,7 +157,7 @@ struct ArenaAllocator
 {
 	inline Allocator allocator;
 	char[] data;
-	usize used;
+	usz used;
 }
 
 /**
diff --git a/lib/std/core/mem_array.c3 b/lib/std/core/mem_array.c3
index 61db68f13..12c38de3e 100644
--- a/lib/std/core/mem_array.c3
+++ b/lib/std/core/mem_array.c3
@@ -4,36 +4,36 @@
 module std::core::mem::array;
 
 /**
- * @require usize.max / elements > $Type.sizeof
+ * @require usz.max / elements > $Type.sizeof
  **/
-macro alloc($Type, usize elements)
+macro alloc($Type, usz elements)
 {
     $Type* ptr = malloc($Type.sizeof * elements);
     return ptr[:elements];
 }
 
 /**
- * @require usize.max / elements > $Type.sizeof
+ * @require usz.max / elements > $Type.sizeof
  **/
-macro talloc($Type, usize elements)
+macro talloc($Type, usz elements)
 {
     $Type* ptr = tmalloc($Type.sizeof * elements, $Type[1].alignof);
     return ptr[:elements];
 }
 
 /**
- * @require (usize.max / elements > $Type.sizeof)
+ * @require (usz.max / elements > $Type.sizeof)
  **/
-macro make($Type, usize elements, Allocator* allocator = mem::current_allocator())
+macro make($Type, usz elements, Allocator* allocator = mem::current_allocator())
 {
     $Type* ptr = allocator.calloc($Type.sizeof * elements)!!;
     return ptr[:elements];
 }
 
 /**
- * @require (usize.max / elements > $Type.sizeof)
+ * @require (usz.max / elements > $Type.sizeof)
  **/
-macro tmake($Type, usize elements)
+macro tmake($Type, usz elements)
 {
     $Type* ptr = tcalloc($Type.sizeof * elements, $Type[1].alignof);
     return ptr[:elements];
diff --git a/lib/std/core/str.c3 b/lib/std/core/str.c3
index 4ef45e3ef..9b62dc47a 100644
--- a/lib/std/core/str.c3
+++ b/lib/std/core/str.c3
@@ -14,7 +14,7 @@ private const uint SURROGATE_HIGH_VALUE = 0xD800;
 fn String join(char[][] s, char[] joiner)
 {
 	if (!s.len) return (String)null;
-	usize total_size = joiner.len * s.len;
+	usz total_size = joiner.len * s.len;
 	foreach (char[]* &str : s)
 	{
 		total_size += str.len;
@@ -29,14 +29,14 @@ fn String join(char[][] s, char[] joiner)
 	return res;
 }
 
-fn usize! str_index_of(char[] s, char[] needle)
+fn usz! str_index_of(char[] s, char[] needle)
 {
-	usize match = 0;
-	usize needed = needle.len;
+	usz match = 0;
+	usz needed = needle.len;
 	if (!needed) return SearchResult.MISSING!;
-	usize index_start = 0;
+	usz index_start = 0;
 	char search = needle[0];
-	foreach (usize i, char c : s)
+	foreach (usz i, char c : s)
 	{
 		if (c == search)
 		{
@@ -57,7 +57,7 @@ fn usize! str_index_of(char[] s, char[] needle)
 
 fn ZString copy_zstring(char[] s)
 {
-    usize len = s.len;
+    usz len = s.len;
     char* str = malloc(len + 1);
     mem::copy(str, s.ptr, len);
     str[len] = 0;
@@ -66,7 +66,7 @@ fn ZString copy_zstring(char[] s)
 
 fn ZString tcopy_zstring(char[] s)
 {
-    usize len = s.len;
+    usz len = s.len;
     char* str = tmalloc(len + 1);
     mem::copy(str, s.ptr, len);
     str[len] = 0;
@@ -91,9 +91,9 @@ fault UnicodeResult
 
 
 
-fn usize utf8_codepoints(char[] utf8)
+fn usz utf8_codepoints(char[] utf8)
 {
-	usize len = 0;
+	usz len = 0;
 	foreach (char c : utf8)
 	{
 		if (c & 0xC0 != 0x80) len++;
@@ -103,7 +103,7 @@ fn usize utf8_codepoints(char[] utf8)
 
 fn Char32[]! utf8to32(char[] utf8, Allocator* allocator = mem::current_allocator)
 {
-	usize codepoints = conv::utf8_codepoints(utf8);
+	usz codepoints = conv::utf8_codepoints(utf8);
 	Char32* data = allocator.alloc(Char32.sizeof * (codepoints + 1))?;
 	conv::utf8to32_unsafe(utf8, data)?;
 	data[codepoints] = 0;
@@ -112,7 +112,7 @@ fn Char32[]! utf8to32(char[] utf8, Allocator* allocator = mem::current_allocator
 
 fn char[] utf32to8(Char32[] utf32, Allocator* allocator = mem::current_allocator)
 {
-	usize len = conv::utf8len_for_utf32(utf32);
+	usz len = conv::utf8len_for_utf32(utf32);
 	char* data = allocator.alloc(len + 1)!!;
 	conv::utf32to8_unsafe(utf32, data);
 	data[len] = 0;
@@ -121,7 +121,7 @@ fn char[] utf32to8(Char32[] utf32, Allocator* allocator = mem::current_allocator
 
 fn Char16[]! utf8to16(char[] utf8, Allocator* allocator = mem::current_allocator)
 {
-	usize len16 = conv::utf16len_for_utf8(utf8);
+	usz len16 = conv::utf16len_for_utf8(utf8);
 	Char16* data = allocator.alloc((len16 + 1) * Char16.sizeof)?;
 	conv::utf8to16_unsafe(utf8, data)?;
 	data[len16] = 0;
@@ -131,7 +131,7 @@ fn Char16[]! utf8to16(char[] utf8, Allocator* allocator = mem::current_allocator
 
 fn char[]! utf16to8(Char16[] utf16, Allocator* allocator = mem::current_allocator())
 {
-	usize len = conv::utf8len_for_utf16(utf16);
+	usz len = conv::utf8len_for_utf16(utf16);
 	char* data = allocator.alloc(len + 1)?;
 	conv::utf16to8_unsafe(utf16, data)?;
 	return data[0 .. len - 1];
@@ -139,23 +139,23 @@ fn char[]! utf16to8(Char16[] utf16, Allocator* allocator = mem::current_allocato
 
 fn char[] copy(char[] s)
 {
-    usize len = s.len;
+    usz len = s.len;
     ZString str_copy = copy_zstring(s) @inline;
     return str_copy[..len];
 }
 
 fn char[] tcopy(char[] s)
 {
-    usize len = s.len;
+    usz len = s.len;
     ZString str_copy = tcopy_zstring(s) @inline;
     return str_copy[..len];
 }
 
 fn char[] tconcat(char[] s1, char[] s2)
 {
-    usize full_len = s1.len + s2.len;
+    usz full_len = s1.len + s2.len;
     char* str = tmalloc(full_len + 1);
-    usize s1_len = s1.len;
+    usz s1_len = s1.len;
     mem::copy(str, s1.ptr, s1_len);
     mem::copy(str + s1_len, s2.ptr, s2.len);
     str[full_len] = 0;
@@ -164,18 +164,18 @@ fn char[] tconcat(char[] s1, char[] s2)
 
 fn char[] concat(char[] s1, char[] s2)
 {
-    usize full_len = s1.len + s2.len;
+    usz full_len = s1.len + s2.len;
     char* str = malloc(full_len + 1);
-    usize s1_len = s1.len;
+    usz s1_len = s1.len;
     mem::copy(str, s1.ptr, s1_len);
     mem::copy(str + s1_len, s2.ptr, s2.len);
     str[full_len] = 0;
     return str[..full_len];
 }
 
-fn usize ZString.len(ZString *str)
+fn usz ZString.len(ZString *str)
 {
-	usize len = 0;
+	usz len = 0;
 	char* ptr = (char*)*str;
 	while (char c = ptr++[0])
 	{
diff --git a/lib/std/core/string.c3 b/lib/std/core/string.c3
index 3b51cc6bc..b45204669 100644
--- a/lib/std/core/string.c3
+++ b/lib/std/core/string.c3
@@ -6,14 +6,14 @@ define String = distinct void*;
 private struct StringData
 {
 	Allocator* allocator;
-	usize len;
-	usize capacity;
+	usz len;
+	usz capacity;
 	char[*] chars;
 }
 
-const usize MIN_CAPACITY = 16;
+const usz MIN_CAPACITY = 16;
 
-fn String new_with_capacity(usize capacity, Allocator* allocator = mem::current_allocator())
+fn String new_with_capacity(usz capacity, Allocator* allocator = mem::current_allocator())
 {
 	if (capacity < MIN_CAPACITY) capacity = MIN_CAPACITY;
 	StringData* data = allocator.alloc(StringData.sizeof + capacity)!!;
@@ -25,7 +25,7 @@ fn String new_with_capacity(usize capacity, Allocator* allocator = mem::current_
 
 fn String new(char[] c)
 {
-	usize len = c.len;
+	usz len = c.len;
 	String str = new_with_capacity(len);
 	StringData* data = str.data();
 	if (len)
@@ -52,7 +52,7 @@ fn ZString String.zstr(String str)
 	return (ZString)&data.chars[0];
 }
 
-fn usize String.len(String this)
+fn usz String.len(String this)
 {
 	if (!this) return 0;
 	return this.data().len;
@@ -61,7 +61,7 @@ fn usize String.len(String this)
 /**
  * @require new_size <= this.len()
  */
-fn void String.chop(String this, usize new_size)
+fn void String.chop(String this, usz new_size)
 {
 	if (!this) return;
 	this.data().len = new_size;
@@ -86,17 +86,17 @@ fn void String.append_utf32(String* str, Char32[] chars)
 /**
  * @require index < str.len()
  **/
-fn void String.set(String str, usize index, char c)
+fn void String.set(String str, usz index, char c)
 {
 	str.data().chars[index] = c;
 }
 
-fn void String.append_repeat(String* str, char c, usize times)
+fn void String.append_repeat(String* str, char c, usz times)
 {
 	if (times == 0) return;
 	str.reserve(times);
 	StringData* data = str.data();
-	for (usize i = 0; i < times; i++)
+	for (usz i = 0; i < times; i++)
 	{
         data.chars[data.len++] = c;
 	}
@@ -155,7 +155,7 @@ fn String String.copy(String* str, Allocator* allocator = null)
 
 fn ZString String.copy_zstr(String* str, Allocator* allocator = mem::current_allocator())
 {
-	usize str_len = str.len();
+	usz str_len = str.len();
 	if (!str_len)
 	{
 		return (ZString)allocator.calloc(1)!!;
@@ -179,7 +179,7 @@ fn bool String.equals(String str, String other_string)
 	if (str1 == str2) return true;
 	if (!str1) return str2.len == 0;
 	if (!str2) return str1.len == 0;
-	usize str1_len = str1.len;
+	usz str1_len = str1.len;
 	if (str1_len != str2.len) return false;
 	for (int i = 0; i < str1_len; i++)
 	{
@@ -204,8 +204,8 @@ fn bool String.less(String str, String other_string)
 	if (str1 == str2) return false;
 	if (!str1) return str2.len != 0;
 	if (!str2) return str1.len == 0;
-	usize str1_len = str1.len;
-	usize str2_len = str2.len;
+	usz str1_len = str1.len;
+	usz str2_len = str2.len;
 	if (str1_len != str2_len) return str1_len < str2_len;
 	for (int i = 0; i < str1_len; i++)
 	{
@@ -216,7 +216,7 @@ fn bool String.less(String str, String other_string)
 
 fn void String.append_chars(String* this, char[] str)
 {
-	usize other_len = str.len;
+	usz other_len = str.len;
 	if (!other_len) return;
 	if (!*this)
 	{
@@ -283,7 +283,7 @@ private fn StringData* String.data(String str) @inline
 	return (StringData*)str;
 }
 
-private fn void String.reserve(String* str, usize addition)
+private fn void String.reserve(String* str, usz addition)
 {
 	StringData* data = str.data();
 	if (!data)
@@ -291,9 +291,9 @@ private fn void String.reserve(String* str, usize addition)
 		*str = string::new_with_capacity(addition);
 		return;
 	}
-	usize len = data.len + addition;
+	usz len = data.len + addition;
 	if (data.capacity >= len) return;
-	usize new_capacity = data.capacity * 2;
+	usz new_capacity = data.capacity * 2;
 	if (new_capacity < MIN_CAPACITY) new_capacity = MIN_CAPACITY;
 	*str = (String)data.allocator.realloc(data, StringData.sizeof + new_capacity)!!;
 }
diff --git a/lib/std/core/string_iterator.c3 b/lib/std/core/string_iterator.c3
index a4e5fc663..201fecff0 100644
--- a/lib/std/core/string_iterator.c3
+++ b/lib/std/core/string_iterator.c3
@@ -5,7 +5,7 @@ module std::core::string::iterator;
 struct StringIterator
 {
 	char[] utf8;
-	usize current;
+	usz current;
 }
 
 fn void StringIterator.reset(StringIterator* this)
@@ -15,10 +15,10 @@ fn void StringIterator.reset(StringIterator* this)
 
 fn Char32! StringIterator.next(StringIterator* this)
 {
-	usize len = this.utf8.len;
-	usize current = this.current;
+	usz len = this.utf8.len;
+	usz current = this.current;
 	if (current >= len) return IteratorResult.NO_MORE_ELEMENT!;
-	usize read = (len - current < 4 ? len - current : 4);
+	usz read = (len - current < 4 ? len - current : 4);
 	Char32 res = conv::utf8_to_char32(&this.utf8[current], &read)?;
 	this.current += read;
 	return res;
diff --git a/lib/std/core/types.c3 b/lib/std/core/types.c3
index e2f360571..559babaf7 100644
--- a/lib/std/core/types.c3
+++ b/lib/std/core/types.c3
@@ -226,5 +226,5 @@ enum TypeKind : char
 struct TypeEnum
 {
 	TypeKind type;
-	usize elements;
+	usz elements;
 }
diff --git a/lib/std/io.c3 b/lib/std/io.c3
index 36b4e4b36..db76bb057 100644
--- a/lib/std/io.c3
+++ b/lib/std/io.c3
@@ -139,7 +139,7 @@ fn bool File.eof(File* file) @inline
 /**
  * @require file && file.file
  */
-fn usize File.read(File* file, void* buffer, usize items, usize element_size = 1)
+fn usz File.read(File* file, void* buffer, usz items, usz element_size = 1)
 {
     return libc::fread(buffer, element_size, items, file.file);
 }
@@ -152,7 +152,7 @@ fn usize File.read(File* file, void* buffer, usize items, usize element_size = 1
  * @require file.file `File must be initialized`
  * @require element_size > 1
  */
-fn usize File.write(File* file, void* buffer, usize items, usize element_size = 1)
+fn usz File.write(File* file, void* buffer, usz items, usz element_size = 1)
 {
     return libc::fwrite(buffer, element_size, items, file.file);
 }
@@ -161,9 +161,9 @@ fn usize File.write(File* file, void* buffer, usize items, usize element_size =
  * @param [&in] file
  * @require file.file `File must be initialized`
  */
-fn usize! File.println(File* file, char[] string)
+fn usz! File.println(File* file, char[] string)
 {
-    usize len = string.len;
+    usz len = string.len;
     if (len != libc::fwrite(string.ptr, 1, len, file.file)) return IoError.UNKNOWN_ERROR!;
     if (!libc::putc('\n', file.file)) return IoError.UNKNOWN_ERROR!;
     return len + 1;
diff --git a/lib/std/io_formatter_private.c3 b/lib/std/io_formatter_private.c3
index 229da00ae..3acc0701f 100644
--- a/lib/std/io_formatter_private.c3
+++ b/lib/std/io_formatter_private.c3
@@ -1,15 +1,15 @@
 module std::io;
 
-private fn void! Formatter.left_adjust(Formatter* this, usize len)
+private fn void! Formatter.left_adjust(Formatter* this, usz len)
 {
 	if (!this.flags.left) return;
-	for (usize l = len; l < this.width; l++) this.out(' ')?;
+	for (usz l = len; l < this.width; l++) this.out(' ')?;
 }
 
-private fn void! Formatter.right_adjust(Formatter* this, usize len)
+private fn void! Formatter.right_adjust(Formatter* this, usz len)
 {
 	if (this.flags.left) return;
-	for (usize l = len; l < this.width; l++) this.out(' ')?;
+	for (usz l = len; l < this.width; l++) this.out(' ')?;
 }
 
 
@@ -126,10 +126,10 @@ private fn FloatType float_from_variant(variant arg)
  * @param maxlen "the maximum len that can be read."
  * @return "The result of the atoi."
  **/
-private fn uint simple_atoi(char* buf, usize maxlen, usize* len_ptr) @inline
+private fn uint simple_atoi(char* buf, usz maxlen, usz* len_ptr) @inline
 {
 	uint i = 0;
-	usize len = *len_ptr;
+	usz len = *len_ptr;
 	while (len < maxlen)
     {
         char c = buf[len];
@@ -144,12 +144,12 @@ private fn uint simple_atoi(char* buf, usize maxlen, usize* len_ptr) @inline
 
 private fn void! Formatter.out_substr(Formatter *this, char[] str)
 {
-	usize l = conv::utf8_codepoints(str);
+	usz l = conv::utf8_codepoints(str);
 	uint prec = this.prec;
 	if (this.flags.precision && l < prec) l = prec;
 	this.right_adjust(' ')?;
-	usize index = 0;
-	usize chars = str.len;
+	usz index = 0;
+	usz chars = str.len;
 	char* ptr = str.ptr;
 	while (index < chars)
 	{
@@ -242,7 +242,7 @@ private fn void! Formatter.etoa(Formatter* this, FloatType value)
 	if (expval) value /= conv.f;
 
 	// output the floating part
-	usize start_idx = this.idx;
+	usz start_idx = this.idx;
 	PrintFlags old = this.flags;
 	this.flags.adapt_exp = false;
 	this.width = fwidth;
@@ -269,7 +269,7 @@ private fn void! Formatter.etoa(Formatter* this, FloatType value)
 private fn void! Formatter.ftoa(Formatter* this, FloatType value)
 {
 	char[PRINTF_FTOA_BUFFER_SIZE] buf = void;
-	usize len = 0;
+	usz len = 0;
 	const FloatType[] POW10 = { 1, 10, 100, 1000, 10000, 100000, 1000000, 10000000, 100000000, 1000000000 };
 	FloatType diff = 0.0;
 
@@ -405,7 +405,7 @@ private fn void! Formatter.ftoa(Formatter* this, FloatType value)
 private fn void! Formatter.ntoa(Formatter* this, NtoaType value, bool negative, uint base)
 {
 	char[PRINTF_NTOA_BUFFER_SIZE] buf = void;
-	usize len = 0;
+	usz len = 0;
 
 	// no hash for 0 values
 	if (!value) this.flags.hash = false;
@@ -426,7 +426,7 @@ private fn void! Formatter.ntoa(Formatter* this, NtoaType value, bool negative,
 	return this.ntoa_format(buf[:PRINTF_NTOA_BUFFER_SIZE], len, negative, base);
 }
 
-private fn void! Formatter.ntoa_format(Formatter* this, char[] buf, usize len, bool negative, uint base)
+private fn void! Formatter.ntoa_format(Formatter* this, char[] buf, usz len, bool negative, uint base)
 {
 	// pad leading zeros
 	if (!this.flags.left)
@@ -529,12 +529,12 @@ private fn void! Formatter.out_char(Formatter* this, variant arg)
 
 private fn void! Formatter.out_reverse(Formatter* this, char[] buf)
 {
-	usize buffer_start_idx = this.idx;
-	usize len = buf.len;
+	usz buffer_start_idx = this.idx;
+	usz len = buf.len;
     // pad spaces up to given width
     if (!this.flags.left && !this.flags.zeropad)
     {
-        for (usize i = len; i < this.width; i++)
+        for (usz i = len; i < this.width; i++)
         {
             this.out(' ')?;
         }
@@ -546,19 +546,19 @@ private fn void! Formatter.out_reverse(Formatter* this, char[] buf)
 	return this.left_adjust(this.idx - buffer_start_idx);
 }
 
-private fn void! printf_advance_format(usize format_len, usize *index_ptr) @inline
+private fn void! printf_advance_format(usz format_len, usz *index_ptr) @inline
 {
-	usize val = ++(*index_ptr);
+	usz val = ++(*index_ptr);
 	if (val >= format_len) return FormattingFault.UNTERMINATED_FORMAT!;
 }
 
-private fn variant! next_variant(variant* args_ptr, usize args_len, usize* arg_index_ptr) @inline
+private fn variant! next_variant(variant* args_ptr, usz args_len, usz* arg_index_ptr) @inline
 {
 	if (*arg_index_ptr >= args_len) return FormattingFault.MISSING_ARG!;
 	return args_ptr[(*arg_index_ptr)++];
 }
 
-private fn int! printf_parse_format_field(variant* args_ptr, usize args_len, usize* args_index_ptr, char* format_ptr, usize format_len, usize* index_ptr) @inline
+private fn int! printf_parse_format_field(variant* args_ptr, usz args_len, usz* args_index_ptr, char* format_ptr, usz format_len, usz* index_ptr) @inline
 {
 	char c = format_ptr[*index_ptr];
 	if (c >= '0' && c <= '9') return simple_atoi(format_ptr, format_len, index_ptr);
diff --git a/lib/std/io_printf.c3 b/lib/std/io_printf.c3
index 2484ab7f2..489c3325f 100644
--- a/lib/std/io_printf.c3
+++ b/lib/std/io_printf.c3
@@ -35,7 +35,7 @@ struct Formatter
 		PrintFlags flags;
     	uint width;
     	uint prec;
-    	usize idx;
+    	usz idx;
 	}
 }
 
@@ -146,7 +146,7 @@ private fn void! Formatter.out_str(Formatter* this, variant arg)
         	return this.out_substr("<variant>");
 		case ENUM:
 			if (this.print_with_function(arg)?) return;
-        	return this.out_substr(arg.type.names[types::variant_to_int(arg, usize)!!]);
+        	return this.out_substr(arg.type.names[types::variant_to_int(arg, usz)!!]);
 		case STRUCT:
 			if (this.print_with_function(arg)?) return;
 			return this.out_substr("<struct>");
@@ -186,12 +186,12 @@ private fn void! Formatter.out_str(Formatter* this, variant arg)
 			if (this.print_with_function(arg)?) return;
 			// this is SomeType[*] so grab the "SomeType"
 			typeid inner = arg.type.inner;
-			usize size = inner.sizeof;
-			usize len = arg.type.len;
+			usz size = inner.sizeof;
+			usz len = arg.type.len;
 			// Pretend this is a char[]
 			void* ptr = (void*)arg.ptr;
 			this.out('[')?;
-			for (usize i = 0; i < len; i++)
+			for (usz i = 0; i < len; i++)
 			{
 				if (i != 0) this.out_substr(", ")?;
 				this.out_str(variant { ptr, inner })?;
@@ -202,12 +202,12 @@ private fn void! Formatter.out_str(Formatter* this, variant arg)
 			if (this.print_with_function(arg)?) return;
 			// this is SomeType[*] so grab the "SomeType"
 			typeid inner = arg.type.inner;
-			usize size = inner.sizeof;
-			usize len = arg.type.len;
+			usz size = inner.sizeof;
+			usz len = arg.type.len;
 			// Pretend this is a char[]
 			void* ptr = (void*)arg.ptr;
 			this.out_substr("[<")?;
-			for (usize i = 0; i < len; i++)
+			for (usz i = 0; i < len; i++)
 			{
 				if (i != 0) this.out_substr(", ")?;
 				this.out_str(variant { ptr, inner })?;
@@ -222,13 +222,13 @@ private fn void! Formatter.out_str(Formatter* this, variant arg)
 			{
 				return this.out_substr(*(char[]*)arg);
 			}
-			usize size = inner.sizeof;
+			usz size = inner.sizeof;
             // Pretend this is a char[]
 			char[]* temp = (void*)arg.ptr;
 			void* ptr = (void*)temp.ptr;
-			usize len = temp.len;
+			usz len = temp.len;
 			this.out('[')?;
-			for (usize i = 0; i < len; i++)
+			for (usz i = 0; i < len; i++)
 			{
 				if (i != 0) this.out_substr(", ")?;
 				this.out_str(variant { ptr, inner })?;
@@ -287,34 +287,34 @@ private fn void! out_string_append_fn(char c, void* data)
 	s.append_char(c);
 }
 
-fn usize! printf(char[] format, args...) @maydiscard
+fn usz! printf(char[] format, args...) @maydiscard
 {
 	Formatter formatter;
 	formatter.init(&out_putchar_fn);
     return formatter.vprintf(format, args);
 }
 
-fn usize! printfln(char[] format, args...) @maydiscard
+fn usz! printfln(char[] format, args...) @maydiscard
 {
 	Formatter formatter;
 	formatter.init(&out_putchar_fn);
-    usize len = formatter.vprintf(format, args)?;
+    usz len = formatter.vprintf(format, args)?;
 	putchar('\n');
 	return len + 1;
 }
 
-fn usize! String.printf(String* str, char[] format, args...) @maydiscard
+fn usz! String.printf(String* str, char[] format, args...) @maydiscard
 {
 	Formatter formatter;
 	formatter.init(&out_string_append_fn, str);
 	return formatter.vprintf(format, args);
 }
 
-fn usize! String.printfln(String* str, char[] format, args...) @maydiscard
+fn usz! String.printfln(String* str, char[] format, args...) @maydiscard
 {
 	Formatter formatter;
 	formatter.init(&out_string_append_fn, str);
-	usize len = formatter.vprintf(format, args)?;
+	usz len = formatter.vprintf(format, args)?;
 	str.append('\n');
 	return len + 1;
 }
@@ -322,7 +322,7 @@ fn usize! String.printfln(String* str, char[] format, args...) @maydiscard
 private struct BufferData
 {
 	char[] buffer;
-	usize written;
+	usz written;
 }
 
 fn char[]! bprintf(char[] buffer, char[] format, args...) @maydiscard
@@ -330,42 +330,42 @@ fn char[]! bprintf(char[] buffer, char[] format, args...) @maydiscard
 	Formatter formatter;
 	BufferData data = { .buffer = buffer };
     formatter.init(&out_buffer_fn, &data);
-    usize size = formatter.vprintf(format, args)?;
+    usz size = formatter.vprintf(format, args)?;
 	return buffer[:size];
 }
 
-fn usize! File.printf(File file, char[] format, args...) @maydiscard
+fn usz! File.printf(File file, char[] format, args...) @maydiscard
 {
 	Formatter formatter;
     formatter.init(&out_putchar_fn, &file);
     return formatter.vprintf(format, args)?;
 }
 
-fn usize! File.printfln(File file, char[] format, args...) @maydiscard
+fn usz! File.printfln(File file, char[] format, args...) @maydiscard
 {
 	Formatter formatter;
     formatter.init(&out_putchar_fn, &file);
-    usize len = formatter.vprintf(format, args)?;
+    usz len = formatter.vprintf(format, args)?;
 	file.putc('\n')?;
 	file.flush();
 	return len + 1;
 }
 
-fn usize! Formatter.printf(Formatter* this, char[] format, args...)
+fn usz! Formatter.printf(Formatter* this, char[] format, args...)
 {
 	return this.vprintf(format, args) @inline;
 }
 
-fn usize! Formatter.vprintf(Formatter* this, char[] format, variant[] variants)
+fn usz! Formatter.vprintf(Formatter* this, char[] format, variant[] variants)
 {
 	if (!this.out_fn)
 	{
 		// use null output function
 		this.out_fn = &out_null_fn;
 	}
-	usize format_len = format.len;
-	usize variant_index = 0;
-	for (usize i = 0; i < format_len; i++)
+	usz format_len = format.len;
+	usz variant_index = 0;
+	for (usz i = 0; i < format_len; i++)
 	{
 		// format specifier?  %[flags][width][.precision][length]
 		char c = format[i];
diff --git a/lib/std/libc.c3 b/lib/std/libc.c3
index c716aa924..213539133 100644
--- a/lib/std/libc.c3
+++ b/lib/std/libc.c3
@@ -53,8 +53,8 @@ extern fn void atexit(TerminateFunction f);
 extern fn void exit(int status);
 extern fn char* getenv(char* name);
 extern fn int system(char* str);
-extern fn void bsearch(void* key, void *base, usize items, usize size, CompareFunction compare);
-extern fn void qsort(void* base, usize items, usize size, CompareFunction compare);
+extern fn void bsearch(void* key, void *base, usz items, usz size, CompareFunction compare);
+extern fn void qsort(void* base, usz items, usz size, CompareFunction compare);
 extern fn int abs(int x);
 extern fn DivResult div(int numer, int denom);
 extern fn long labs(long x);
@@ -65,33 +65,33 @@ extern fn void srand(uint seed);
 // MB functions omitted
 
 // string
-extern fn void* memchr(void* str, int c, usize n);
-extern fn int memcmp(void* str1, void* str2, usize n);
-extern fn void* memcpy(void* dest, void* src, usize n);
-extern fn void* memmove(void* dest, void* src, usize n);
-extern fn void* memset(void* dest, usize n);
+extern fn void* memchr(void* str, int c, usz n);
+extern fn int memcmp(void* str1, void* str2, usz n);
+extern fn void* memcpy(void* dest, void* src, usz n);
+extern fn void* memmove(void* dest, void* src, usz n);
+extern fn void* memset(void* dest, usz n);
 extern fn char* strcat(char* dest, char* src);
-extern fn char* strncat(char* dest, char* src, usize n);
+extern fn char* strncat(char* dest, char* src, usz n);
 extern fn char* strchr(char* str, int c);
 extern fn int strcmp(char* str1, char* str2);
-extern fn int strncmp(char* str1, char* str2, usize n);
+extern fn int strncmp(char* str1, char* str2, usz n);
 extern fn int strcoll(char* str1, char* str2);
 extern fn char* strcpy(char* dst, char* src);
-extern fn char* strncpy(char* dst, char* src, usize n);
-extern fn usize strcspn(char* str1, char* str2);
+extern fn char* strncpy(char* dst, char* src, usz n);
+extern fn usz strcspn(char* str1, char* str2);
 extern fn char* strerror(int errn);
-extern fn usize strlen(char* str);
+extern fn usz strlen(char* str);
 extern fn char* strpbrk(char* str1, char* str2);
-extern fn usize strspn(char* str1, char* str2);
+extern fn usz strspn(char* str1, char* str2);
 extern fn char* strstr(char* haystack, char* needle);
 extern fn char* strtok(char* str, char* delim);
-extern fn usize strxfrm(char* dest, char* src, usize n);
+extern fn usz strxfrm(char* dest, char* src, usz n);
 
 // malloc
-extern fn void* malloc(usize size);
-extern fn void* calloc(usize count, usize size);
+extern fn void* malloc(usz size);
+extern fn void* calloc(usz count, usz size);
 extern fn void* free(void*);
-extern fn void* realloc(void* ptr, usize size);
+extern fn void* realloc(void* ptr, usz size);
 
 // stdio
 
@@ -103,9 +103,9 @@ $case OsType.LINUX:
     extern CFile __stdin @extname("stdin");
     extern CFile __stdout @extname("stdout");
     extern CFile __stderr @extname("stderr");
-    extern fn usize malloc_usable_size(void* ptr);
-    macro usize malloc_size(void* ptr) { return malloc_usable_size(ptr); }
-	extern fn void* aligned_alloc(usize align, usize size);
+    extern fn usz malloc_usable_size(void* ptr);
+    macro usz malloc_size(void* ptr) { return malloc_usable_size(ptr); }
+	extern fn void* aligned_alloc(usz align, usz size);
     macro CFile stdin() { return __stdin; }
     macro CFile stdout() { return __stdout; }
     macro CFile stderr() { return __stderr; }
@@ -113,15 +113,15 @@ $case OsType.MACOSX:
     extern CFile __stdinp;
     extern CFile __stdoutp;
     extern CFile __stderrp;
-    extern fn usize malloc_size(void* ptr);
-    extern fn void* aligned_alloc(usize align, usize size);
+    extern fn usz malloc_size(void* ptr);
+    extern fn void* aligned_alloc(usz align, usz size);
 	macro CFile stdin() { return __stdinp; }
     macro CFile stdout() { return __stdoutp; }
     macro CFile stderr() { return __stderrp; }
 $case OsType.WIN32:
     extern fn CFile __acrt_iob_func(CInt c);
-    extern fn usize _msize(void* ptr);
-    macro usize malloc_size(void* ptr) { return _msize(ptr); }
+    extern fn usz _msize(void* ptr);
+    macro usz malloc_size(void* ptr) { return _msize(ptr); }
     macro CFile stdin() { return __acrt_iob_func(0); }
     macro CFile stdout() { return __acrt_iob_func(1); }
     macro CFile stderr() { return __acrt_iob_func(2); }
@@ -159,22 +159,22 @@ extern fn int ferror(CFile stream);
 extern fn int fflush(CFile stream);
 extern fn int fgetpos(CFile stream, Fpos* pos);
 extern fn CFile fopen(char* filename, char* mode);
-extern fn usize fread(void* ptr, usize size, usize nmemb, CFile stream);
+extern fn usz fread(void* ptr, usz size, usz nmemb, CFile stream);
 extern fn CFile freopen(char* filename, char* mode, CFile stream);
 extern fn int fseek(CFile stream, SeekIndex offset, int whence);
 extern fn int fsetpos(CFile stream, Fpos* pos);
 extern fn SeekIndex ftell(CFile stream);
-extern fn usize fwrite(void* ptr, usize size, usize nmemb, CFile stream);
+extern fn usz fwrite(void* ptr, usz size, usz nmemb, CFile stream);
 extern fn int remove(char* filename);
 extern fn int rename(char* old_name, char* new_name);
 extern fn void rewind(CFile stream);
 extern fn void setbuf(CFile stream, char* buffer);
-extern fn void setvbuf(CFile stream, char* buffer, int mode, usize size);
+extern fn void setvbuf(CFile stream, char* buffer, int mode, usz size);
 extern fn CFile tmpnam(char* str);
 extern fn int fprintf(CFile stream, char* format, ...);
 extern fn int printf(char* format, ...);
 extern fn int sprintf(char* str, char* format, ...);
-extern fn int snprintf(char* str, usize size, char* format, ...);
+extern fn int snprintf(char* str, usz size, char* format, ...);
 extern fn int fscanf(CFile stream, char* format, ...);
 extern fn int scanf(char* format, ...);
 extern fn int sscanf(char* str, char* format, ...);
@@ -188,7 +188,7 @@ extern fn int putchar(int c);
 extern fn int puts(char* str);
 extern fn int ungetc(int c, CFile stream);
 extern fn void perror(char* str);
-extern fn isize getline(char** linep, usize* linecapp, CFile stream);
+extern fn isz getline(char** linep, usz* linecapp, CFile stream);
 
 // vsprintf vprintf not supported
 
@@ -225,7 +225,7 @@ extern fn double difftime(Time time1, Time time2);
 extern fn Tm* gmtime(Time *timer);
 extern fn Tm* localtime(Time *timer);
 extern fn Time mktime(Tm *timeptr);
-extern fn usize strftime(char* str, usize maxsize, char* format, Tm *timeptr);
+extern fn usz strftime(char* str, usz maxsize, char* format, Tm *timeptr);
 extern fn Time time(Time *timer);
 
 // signal
diff --git a/lib/std/linkedlist.c3 b/lib/std/linkedlist.c3
index 9513f8454..af2ebd0fb 100644
--- a/lib/std/linkedlist.c3
+++ b/lib/std/linkedlist.c3
@@ -12,7 +12,7 @@ private struct Node
 
 struct LinkedList
 {
-    usize size;
+    usz size;
     Node *first;
     Node *last;
 }
@@ -69,12 +69,12 @@ fn void LinkedList.free(LinkedList *list)
     list.size = 0;
 }
 
-fn usize LinkedList.len(LinkedList* list) @inline
+fn usz LinkedList.len(LinkedList* list) @inline
 {
     return list.size;
 }
 
-fn Type LinkedList.get(LinkedList* list, usize index)
+fn Type LinkedList.get(LinkedList* list, usz index)
 {
     Node* node = list.first;
     while (index--)
diff --git a/lib/std/list.c3 b/lib/std/list.c3
index 62853688a..8f53f9ac8 100644
--- a/lib/std/list.c3
+++ b/lib/std/list.c3
@@ -5,8 +5,8 @@ module std::array::list<Type>;
 
 struct List
 {
-    usize size;
-    usize capacity;
+    usz size;
+    usz capacity;
     Type *entries;
 }
 
@@ -49,9 +49,9 @@ fn Type List.pop_first(List *list)
     return value;
 }
 
-fn void List.remove_at(List *list, usize index)
+fn void List.remove_at(List *list, usz index)
 {
-    for (usize i = index + 1; i < list.size; i++)
+    for (usz i = index + 1; i < list.size; i++)
     {
         list.entries[i - 1] = list.entries[i];
     }
@@ -63,10 +63,10 @@ fn void List.push_front(List *list, Type type) @inline
     list.insert_at(0, type);
 }
 
-fn void List.insert_at(List* list, usize index, Type type)
+fn void List.insert_at(List* list, usz index, Type type)
 {
     list.ensure_capacity();
-    for (usize i = list.size; i > index; i--)
+    for (usz i = list.size; i > index; i--)
     {
         list.entries[i] = list.entries[i - 1];
     }
@@ -99,12 +99,12 @@ fn bool List.is_empty(List *list)
     return !list.size;
 }
 
-fn usize List.len(List *list) @operator(len)
+fn usz List.len(List *list) @operator(len)
 {
     return list.size;
 }
 
-fn Type List.get(List *list, usize index)
+fn Type List.get(List *list, usz index)
 {
     return list.entries[index];
 }
@@ -117,17 +117,17 @@ fn void List.free(List *list)
     list.entries = null;
 }
 
-fn void List.swap(List *list, usize i, usize j)
+fn void List.swap(List *list, usz i, usz j)
 {
 	@swap(list.entries[i], list.entries[j]);
 }
 
-macro Type List.@item_at(List &list, usize index) @operator([])
+macro Type List.@item_at(List &list, usz index) @operator([])
 {
     return list.entries[index];
 }
 
-macro Type* List.@item_ref(List &list, usize index) @operator(&[])
+macro Type* List.@item_ref(List &list, usz index) @operator(&[])
 {
     return &list.entries[index];
 }
diff --git a/lib/std/map.c3 b/lib/std/map.c3
index 3d65ea58d..c6a824820 100644
--- a/lib/std/map.c3
+++ b/lib/std/map.c3
@@ -122,7 +122,7 @@ fn Key[] HashMap.key_list(HashMap* map, Allocator* allocator = mem::temp_allocat
 	if (!map.count) return Key[] {};
 
 	Key[] list = array::make(Key, map.count, allocator);
-	usize index = 0;
+	usz index = 0;
 	foreach (Entry* entry : map.table)
 	{
 		while (entry)
@@ -138,7 +138,7 @@ fn Value[] HashMap.value_list(HashMap* map, Allocator* allocator = mem::temp_all
 {
 	if (!map.count) return Value[] {};
 	Value[] list = array::make(Value, map.count, allocator);
-	usize index = 0;
+	usz index = 0;
 	foreach (Entry* entry : map.table)
 	{
 		while (entry)
diff --git a/lib/std/priorityqueue.c3 b/lib/std/priorityqueue.c3
index 50ef511ef..483ea8a8f 100644
--- a/lib/std/priorityqueue.c3
+++ b/lib/std/priorityqueue.c3
@@ -34,10 +34,10 @@ struct PriorityQueue
 fn void PriorityQueue.push(PriorityQueue* pq, Type element)
 {
 	pq.heap.push(element);
-	usize i = pq.heap.len() - 1;
+	usz i = pq.heap.len() - 1;
 	while (i > 0)
 	{
-		usize parent = (i - 1) / 2;
+		usz parent = (i - 1) / 2;
 		if ((pq.max && greater(pq.heap.get(i), pq.heap.get(parent))) || (!pq.max && less(pq.heap.get(i), pq.heap.get(parent))))
 		{
 			pq.heap.swap(i, parent);
@@ -53,14 +53,14 @@ fn void PriorityQueue.push(PriorityQueue* pq, Type element)
 */
 fn Type! PriorityQueue.pop(PriorityQueue* pq)
 {
-	usize i = 0;
-	usize len = pq.heap.len() @inline;
+	usz i = 0;
+	usz len = pq.heap.len() @inline;
 	if (!len) return IteratorResult.NO_MORE_ELEMENT!;
-	usize newCount = len - 1;
+	usz newCount = len - 1;
 	pq.heap.swap(0, newCount);
 	while ((2 * i + 1) < newCount)
 	{
-		usize j = 2 * i + 1;
+		usz j = 2 * i + 1;
 		if (((j + 1) < newCount) &&
 			((pq.max && greater(pq.heap.get(j + 1), pq.heap[j]))
 				|| (!pq.max && less(pq.heap.get(j + 1), pq.heap.get(j)))))
@@ -99,7 +99,7 @@ fn void PriorityQueue.free(PriorityQueue* pq)
 /**
  * @require pq != null
  */
-fn usize PriorityQueue.len(PriorityQueue* pq) @operator(len)
+fn usz PriorityQueue.len(PriorityQueue* pq) @operator(len)
 {
 	return pq.heap.len();
 }
diff --git a/lib/std/runtime.c3 b/lib/std/runtime.c3
index e4fe95fdb..a1e02ea15 100644
--- a/lib/std/runtime.c3
+++ b/lib/std/runtime.c3
@@ -18,13 +18,13 @@ struct VirtualContainer
 struct SubArrayContainer
 {
     void* ptr;
-    usize len;
+    usz len;
 }
 
 struct VarArrayHeader
 {
-    usize size;
-    usize capacity;
+    usz size;
+    usz capacity;
     void *allocator;
 }
 
diff --git a/src/compiler/compiler_internal.h b/src/compiler/compiler_internal.h
index ced0454ff..bf7a69d2b 100644
--- a/src/compiler/compiler_internal.h
+++ b/src/compiler/compiler_internal.h
@@ -1797,8 +1797,8 @@ extern TypeInfo *poisoned_type_info;
 
 extern Type *type_bool, *type_void, *type_voidptr;
 extern Type *type_float16, *type_float, *type_double, *type_f128;
-extern Type *type_ichar, *type_short, *type_int, *type_long, *type_isize;
-extern Type *type_char, *type_ushort, *type_uint, *type_ulong, *type_usize;
+extern Type *type_ichar, *type_short, *type_int, *type_long, *type_isize, *type_isz;
+extern Type *type_char, *type_ushort, *type_uint, *type_ulong, *type_usize, *type_usz;
 extern Type *type_iptr, *type_uptr, *type_iptrdiff, *type_uptrdiff;
 extern Type *type_u128, *type_i128;
 extern Type *type_typeid, *type_anyerr, *type_typeinfo, *type_member;
diff --git a/src/compiler/enums.h b/src/compiler/enums.h
index 9688a886c..d154fe017 100644
--- a/src/compiler/enums.h
+++ b/src/compiler/enums.h
@@ -463,6 +463,7 @@ typedef enum
 	TOKEN_IPTR,
 	TOKEN_IPTRDIFF,
 	TOKEN_ISIZE,
+	TOKEN_ISZ,
 	TOKEN_LONG,
 	TOKEN_SHORT,
 	TOKEN_UINT128,
@@ -472,6 +473,7 @@ typedef enum
 	TOKEN_UPTRDIFF,
 	TOKEN_USHORT,
 	TOKEN_USIZE,
+	TOKEN_USZ,
 	TOKEN_FLOAT128,
 	TOKEN_VARIANT,
 	TOKEN_ANYERR,
@@ -595,8 +597,8 @@ typedef enum
   case TOKEN_FLOAT16: case TOKEN_INT128: case TOKEN_ICHAR: case TOKEN_INT: \
   case TOKEN_IPTR: case TOKEN_IPTRDIFF: case TOKEN_ISIZE: case TOKEN_LONG: \
   case TOKEN_SHORT: case TOKEN_UINT128: case TOKEN_UINT: case TOKEN_ULONG:  \
-  case TOKEN_UPTR: case TOKEN_UPTRDIFF: case TOKEN_USHORT: case TOKEN_USIZE:  \
-  case TOKEN_FLOAT128: case TOKEN_TYPEID: case TOKEN_ANYERR: case TOKEN_VARIANT
+  case TOKEN_UPTR: case TOKEN_UPTRDIFF: case TOKEN_USHORT: case TOKEN_USIZE:\
+  case TOKEN_USZ: case TOKEN_ISZ: case TOKEN_FLOAT128: case TOKEN_TYPEID: case TOKEN_ANYERR: case TOKEN_VARIANT
 #define TYPE_TOKENS NON_VOID_TYPE_TOKENS: case TOKEN_VOID
 #define TYPELIKE_TOKENS TYPE_TOKENS: case TOKEN_TYPE_IDENT: \
 	case TOKEN_CT_TYPE_IDENT: case TOKEN_CT_TYPEOF: case TOKEN_CT_EVALTYPE: \
diff --git a/src/compiler/parse_expr.c b/src/compiler/parse_expr.c
index 24180bf35..9eea64a8d 100644
--- a/src/compiler/parse_expr.c
+++ b/src/compiler/parse_expr.c
@@ -1680,6 +1680,8 @@ ParseRule rules[TOKEN_EOF + 1] = {
 		[TOKEN_UINT128] = { parse_type_identifier, NULL, PREC_NONE },
 		[TOKEN_ISIZE] = { parse_type_identifier, NULL, PREC_NONE },
 		[TOKEN_USIZE] = { parse_type_identifier, NULL, PREC_NONE },
+		[TOKEN_ISZ] = { parse_type_identifier, NULL, PREC_NONE },
+		[TOKEN_USZ] = { parse_type_identifier, NULL, PREC_NONE },
 		[TOKEN_IPTR] = { parse_type_identifier, NULL, PREC_NONE },
 		[TOKEN_UPTR] = { parse_type_identifier, NULL, PREC_NONE },
 		[TOKEN_IPTRDIFF] = { parse_type_identifier, NULL, PREC_NONE },
diff --git a/src/compiler/tokens.c b/src/compiler/tokens.c
index 923ca7db9..2ad6eb844 100644
--- a/src/compiler/tokens.c
+++ b/src/compiler/tokens.c
@@ -307,6 +307,10 @@ const char *token_type_to_string(TokenType type)
 			return "isize";
 		case TOKEN_USIZE:
 			return "usize";
+		case TOKEN_ISZ:
+			return "isz";
+		case TOKEN_USZ:
+			return "usz";
 		case TOKEN_IPTR:
 			return "iptr";
 		case TOKEN_UPTR:
diff --git a/src/compiler/types.c b/src/compiler/types.c
index ac72889e4..6e2ce7e31 100644
--- a/src/compiler/types.c
+++ b/src/compiler/types.c
@@ -11,7 +11,7 @@ static struct
 	Type u0, u1, i8, i16, i32, i64, i128, ixx;
 	Type u8, u16, u32, u64, u128;
 	Type f16, f32, f64, f128, fxx;
-	Type usz, isz, uptr, iptr, uptrdiff, iptrdiff;
+	Type usz, isz, usize, isize, uptr, iptr, uptrdiff, iptrdiff;
 	Type voidstar, typeid, anyerr, member, typeinfo, untyped_list;
 	Type any, anyfail;
 } t;
@@ -33,7 +33,8 @@ Type *type_long = &t.i64;
 Type *type_i128 = &t.i128;
 Type *type_iptr = &t.iptr;
 Type *type_iptrdiff = &t.iptrdiff;
-Type *type_isize = &t.isz;
+Type *type_isize = &t.isize;
+Type *type_isz = &t.isz;
 Type *type_char = &t.u8;
 Type *type_ushort = &t.u16;
 Type *type_uint = &t.u32;
@@ -41,7 +42,8 @@ Type *type_ulong = &t.u64;
 Type *type_u128 = &t.u128;
 Type *type_uptr = &t.uptr;
 Type *type_uptrdiff = &t.uptrdiff;
-Type *type_usize = &t.usz;
+Type *type_usize = &t.usize;
+Type *type_usz = &t.usz;
 Type *type_anyerr = &t.anyerr;
 Type *type_untypedlist = &t.untyped_list;
 Type *type_anyfail = &t.anyfail;
@@ -1436,8 +1438,10 @@ void type_setup(PlatformTarget *target)
 	t.voidstar.pointer = type_void;
 	type_init("variant", &t.any, TYPE_ANY, target->width_pointer * 2, target->align_pointer);
 
-	type_create_alias("usize", &t.usz, type_int_unsigned_by_bitsize(target->width_pointer));
-	type_create_alias("isize", &t.isz, type_int_signed_by_bitsize(target->width_pointer));
+	type_create_alias("usize", &t.usize, type_int_unsigned_by_bitsize(target->width_pointer));
+	type_create_alias("isize", &t.isize, type_int_signed_by_bitsize(target->width_pointer));
+	type_create_alias("usz", &t.usz, type_int_unsigned_by_bitsize(target->width_pointer));
+	type_create_alias("isz", &t.isz, type_int_signed_by_bitsize(target->width_pointer));
 	type_create_alias("uptr", &t.uptr, type_int_unsigned_by_bitsize(target->width_pointer));
 	type_create_alias("iptr", &t.iptr, type_int_signed_by_bitsize(target->width_pointer));
 
@@ -1583,6 +1587,8 @@ Type *type_from_token(TokenType type)
 			return type_iptrdiff;
 		case TOKEN_ISIZE:
 			return type_isize;
+		case TOKEN_ISZ:
+			return type_isz;
 		case TOKEN_LONG:
 			return type_long;
 		case TOKEN_SHORT:
@@ -1601,6 +1607,8 @@ Type *type_from_token(TokenType type)
 			return type_ushort;
 		case TOKEN_USIZE:
 			return type_usize;
+		case TOKEN_USZ:
+			return type_usz;
 		case TOKEN_TYPEID:
 			return type_typeid;
 		default: