diff --git a/lib/std/io/formatter_private.c3 b/lib/std/io/formatter_private.c3
index dbaf5f035..3a7ed5363 100644
--- a/lib/std/io/formatter_private.c3
+++ b/lib/std/io/formatter_private.c3
@@ -52,7 +52,7 @@ fn uint128? int_from_any(any arg, bool *is_neg) @private
 	switch (arg.type)
 	{
 		case bool:
-			return *(uint128*)arg;
+			return (uint128)*(bool*)arg;
 		case ichar:
 			int val = *(ichar*)arg;
 			return (*is_neg = val < 0) ? (~(uint128)val) + 1 : (uint128)val;
diff --git a/lib/std/io/io.c3 b/lib/std/io/io.c3
index 8bfe75985..8023b89e3 100644
--- a/lib/std/io/io.c3
+++ b/lib/std/io/io.c3
@@ -139,7 +139,7 @@ macro usz? fprint(out, x)
  @param [in] format : `The printf-style format string`
  @return `the number of characters printed`
 *>
-fn usz? fprintf(OutStream out, String format, args...)
+fn usz? fprintf(OutStream out, String format, args...) @format(1)
 {
 	Formatter formatter;
 	formatter.init(&out_putstream_fn, &out);
@@ -154,7 +154,7 @@ fn usz? fprintf(OutStream out, String format, args...)
  @param [in] format : `The printf-style format string`
  @return `the number of characters printed`
 *>
-fn usz? fprintfn(OutStream out, String format, args...) @maydiscard
+fn usz? fprintfn(OutStream out, String format, args...) @format(1) @maydiscard
 {
 	Formatter formatter;
 	formatter.init(&out_putstream_fn, &out);
@@ -249,7 +249,7 @@ fn void? out_putchar_fn(void* data @unused, char c) @private
  @param [in] format : `The printf-style format string`
  @return `the number of characters printed`
 *>
-fn usz? printf(String format, args...) @maydiscard
+fn usz? printf(String format, args...) @format(0) @maydiscard
 {
 	Formatter formatter;
 	formatter.init(&out_putchar_fn);
@@ -263,7 +263,7 @@ fn usz? printf(String format, args...) @maydiscard
  @param [in] format : `The printf-style format string`
  @return `the number of characters printed`
 *>
-fn usz? printfn(String format, args...) @maydiscard
+fn usz? printfn(String format, args...) @format(0) @maydiscard
 {
 	Formatter formatter;
 	formatter.init(&out_putchar_fn);
diff --git a/releasenotes.md b/releasenotes.md
index f2c0556bd..21744252b 100644
--- a/releasenotes.md
+++ b/releasenotes.md
@@ -43,7 +43,8 @@
 - Use `@pool_init()` to set up a temp pool on a thread. Only the main thread has implicit temp pool setup.
 - `tmem` is now a variable.
 - Compile test and benchmark functions when invoking `--lsp` #2058.
- 
+- Added `@format` attribute for compile time printf validation #2057.
+
 ### Fixes
 - Fix address sanitizer to work on MachO targets (e.g. MacOS).
 - Post and pre-decrement operators switched places for vector elements #2010.
@@ -57,6 +58,7 @@
 - Bug due to missing cast when doing `$i[$x] = $z`.
 - Incorrectly allowed getting pointer to a macro #2049.
 - &self not runtime null-checked in macro #1827.
+- Bug when printing a boolean value as an integer using printf.
 
 ### Stdlib changes
 - `new_*` functions in general moved to version without `new_` prefix.
diff --git a/src/compiler/compiler_internal.h b/src/compiler/compiler_internal.h
index 4048cd02d..d3469013a 100644
--- a/src/compiler/compiler_internal.h
+++ b/src/compiler/compiler_internal.h
@@ -254,6 +254,7 @@ typedef struct
 	bool is_pure : 1;
 	bool noreturn : 1;
 	bool always_const : 1;
+	uint8_t format : 8;
 } CalleeAttributes;
 
 typedef struct
diff --git a/src/compiler/enums.h b/src/compiler/enums.h
index d3c65ca74..85fb351fd 100644
--- a/src/compiler/enums.h
+++ b/src/compiler/enums.h
@@ -275,6 +275,7 @@ typedef enum
 	ATTRIBUTE_EXPORT,
 	ATTRIBUTE_EXTERN,
 	ATTRIBUTE_FINALIZER,
+	ATTRIBUTE_FORMAT,
 	ATTRIBUTE_IF,
 	ATTRIBUTE_INLINE,
 	ATTRIBUTE_INIT,
diff --git a/src/compiler/sema_decls.c b/src/compiler/sema_decls.c
index f20d245de..8005c1d60 100755
--- a/src/compiler/sema_decls.c
+++ b/src/compiler/sema_decls.c
@@ -1097,6 +1097,7 @@ static inline bool sema_analyse_signature(SemaContext *context, Signature *sig,
 	// Check return type
 	ASSERT(sig->rtype || sig->is_macro);
 	Type *rtype = NULL;
+	int format_index = (int)sig->attrs.format - 1;
 	if (sig->rtype)
 	{
 		TypeInfo *rtype_info = type_infoptr(sig->rtype);
@@ -1180,6 +1181,22 @@ static inline bool sema_analyse_signature(SemaContext *context, Signature *sig,
 								type_to_error_string(method_parent->type), decl->name, type_to_error_string(method_parent->type));
 	}
 
+	if (format_index >= 0)
+	{
+		if (format_index >= param_count)
+		{
+			RETURN_SEMA_ERROR(decl, "The format '@format()' index was out of range.");
+		}
+		if (sig->variadic != VARIADIC_ANY)
+		{
+			RETURN_SEMA_ERROR(decl, "'@format()' is only valid for a function or macro with 'args...' style vaargs.");
+		}
+		if (sig->vararg_index == format_index)
+		{
+			RETURN_SEMA_ERROR(decl, "The format string cannot be a vaarg parameter.");
+		}
+	}
+
 	// Check parameters
 	for (unsigned i = 0; i < param_count; i++)
 	{
@@ -1231,6 +1248,15 @@ static inline bool sema_analyse_signature(SemaContext *context, Signature *sig,
 			                                     : RESOLVE_TYPE_DEFAULT)) return decl_poison(param);
 			param->type = type_info->type;
 		}
+		if (i == format_index)
+		{
+			if (!type_info || type_info->type->canonical != type_string)
+			{
+				SourceSpan span = type_info ? type_info->span : param->span;
+				sema_error_at(context, span, "The '@format()' format string must be be of type 'String'.");
+				return decl_poison(param);
+			}
+		}
 		if (type_info && param->var.no_alias && !type_is_pointer(param->type) && type_flatten(param->type)->type_kind != TYPE_SLICE)
 		{
 			SEMA_ERROR(param, "The parameter was set to @noalias, but it was neither a slice nor a pointer. You need to either remove '@noalias' or use pointer/slice type.");
@@ -1239,6 +1265,11 @@ static inline bool sema_analyse_signature(SemaContext *context, Signature *sig,
 		switch (var_kind)
 		{
 			case VARDECL_PARAM_EXPR:
+				if (i == format_index)
+				{
+					SEMA_ERROR(param, "'@format()' cannot be used with lazy arguments, please remove '@format' or make this a regular parameter.");
+					return decl_poison(param);
+				}
 				if (!is_macro)
 				{
 					SEMA_ERROR(param, "Only regular parameters are allowed for functions.");
@@ -2486,6 +2517,7 @@ static bool sema_analyse_attribute(SemaContext *context, ResolvedAttrData *attr_
 			[ATTRIBUTE_EXPORT] = ATTR_FUNC | ATTR_GLOBAL | ATTR_CONST | USER_DEFINED_TYPES | ATTR_ALIAS,
 			[ATTRIBUTE_EXTERN] = ATTR_FUNC | ATTR_GLOBAL | ATTR_CONST | USER_DEFINED_TYPES,
 			[ATTRIBUTE_FINALIZER] = ATTR_FUNC,
+			[ATTRIBUTE_FORMAT] = ATTR_FUNC | ATTR_MACRO | ATTR_FNTYPE,
 			[ATTRIBUTE_IF] = (AttributeDomain)~(ATTR_CALL | ATTR_LOCAL | ATTR_PARAM),
 			[ATTRIBUTE_INIT] = ATTR_FUNC,
 			[ATTRIBUTE_INLINE] = ATTR_FUNC | ATTR_CALL,
@@ -2740,6 +2772,37 @@ static bool sema_analyse_attribute(SemaContext *context, ResolvedAttrData *attr_
 			decl->func_decl.attr_finalizer = true;
 			// Ugly
 			goto PARSE;
+		case ATTRIBUTE_FORMAT:
+			if (args != 1) RETURN_SEMA_ERROR(attr, "'@format' expects the index of the format string as the argument, e.g. '@format(1)'.");
+			if (!sema_analyse_expr(context, expr)) return false;
+			if (!type_is_integer(expr->type) || !sema_cast_const(expr))
+			{
+				RETURN_SEMA_ERROR(expr, "Expected an integer compile time constant value.");
+			}
+			else
+			{
+				Int i = expr->const_expr.ixx;
+				if (int_is_neg(i) || int_icomp(i, 127, BINARYOP_GT))
+				{
+					RETURN_SEMA_ERROR(expr, "The index must be between 0 and 127.");
+				}
+				uint16_t val = (uint16_t)i.i.low;
+				switch (decl->decl_kind)
+				{
+					case DECL_FUNC:
+					case DECL_MACRO:
+						if (decl->func_decl.signature.attrs.format) break;
+						decl->func_decl.signature.attrs.format = val + 1;
+						return true;
+					case DECL_FNTYPE:
+						if (decl->fntype_decl.attrs.format) break;
+						decl->fntype_decl.attrs.format = val + 1;
+						return true;
+					default:
+						UNREACHABLE;
+				}
+				RETURN_SEMA_ERROR(attr, "'@format' may not appear twice.");
+			}
 		case ATTRIBUTE_LINK:
 			if (args < 1) RETURN_SEMA_ERROR(attr, "'@link' requires at least one argument.");
 			Expr *cond = args > 1 ? attr->exprs[0] : NULL;
diff --git a/src/compiler/sema_expr.c b/src/compiler/sema_expr.c
index a98f8827a..b87320a45 100644
--- a/src/compiler/sema_expr.c
+++ b/src/compiler/sema_expr.c
@@ -1518,7 +1518,7 @@ INLINE bool sema_call_evaluate_arguments(SemaContext *context, CalledDecl *calle
 	unsigned vaarg_index = sig->vararg_index;
 	Variadic variadic = sig->variadic;
 	Decl **decl_params = callee->params;
-
+	int format_index = (int)sig->attrs.format - 1;
 	// If this is a type call, then we have an implicit first argument.
 	if (callee->struct_var)
 	{
@@ -1811,6 +1811,97 @@ SPLAT_NORMAL:;
 		RETURN_SEMA_FUNC_ERROR(callee->definition, call, "The parameter '%s' must be set, did you forget it?", param->name);
 	}
 	call->call_expr.arguments = actual_args;
+	if (format_index >= 0) goto CHECK_FORMAT;
+	return true;
+CHECK_FORMAT:;
+	// Check
+	Expr *expr = actual_args[format_index];
+	if (!sema_cast_const(expr) || call->call_expr.va_is_splat) return true;
+	assert(expr_is_const_string(expr));
+	const char *data = expr->const_expr.bytes.ptr;
+	size_t len = expr->const_expr.bytes.len;
+	size_t idx = 0;
+	Expr **vaargs = call->call_expr.varargs;
+	unsigned vacount = vec_size(vaargs);
+	for (size_t i = 0; i < len; i++)
+	{
+		if (data[i] != '%') continue;
+		i++;
+		char c = data[i];
+		if (c == '%') continue;
+		if (idx == vacount)
+		{
+			RETURN_SEMA_FUNC_ERROR(callee->definition, call, "Too few arguments provided for the formatting string.");
+		}
+		if (c == '.' && data[++i] == '*')
+		{
+			idx++;
+		}
+		expr = vaargs[idx];
+		assert(expr->expr_kind == EXPR_MAKE_ANY);
+		Type *type = expr->make_any_expr.typeid->const_expr.typeid;
+		type = type_flatten(type);
+		while (true)
+		{
+			switch (c)
+			{
+				case 's':
+					goto NEXT;
+				case 'c':
+					if (!type_is_integer(type))
+					{
+						RETURN_SEMA_ERROR(vaargs[idx], "Expected an integer here.");
+					}
+					goto NEXT;
+				case 'd':
+				case 'X':
+				case 'x':
+				case 'B':
+				case 'b':
+				case 'o':
+				case 'a':
+				case 'A':
+				case 'F':
+				case 'f':
+				case 'e':
+				case 'E':
+				case 'g':
+				case 'G':
+					if (!type_is_number_or_bool(type))
+					{
+						RETURN_SEMA_ERROR(vaargs[idx], "Expected a number here, but was %s", type_quoted_error_string(type));
+					}
+					goto NEXT;
+				case 'p':
+					if (!type_is_pointer(type) && !type_is_integer(type))
+					{
+						RETURN_SEMA_ERROR(vaargs[idx], "Expected a pointer here.");
+					}
+					goto NEXT;
+				case 'H':
+				case 'h':
+					if (!type_flat_is_char_array(type))
+					{
+						RETURN_SEMA_ERROR(vaargs[idx], "Expected a char array here.");
+					}
+					goto NEXT;
+				case '\0':
+					goto DONE;
+				case '+':
+				case '-':
+				default:
+					break;
+			}
+			c = data[++i];
+		}
+NEXT:
+		idx++;
+	}
+DONE:
+	if (idx < vacount)
+	{
+		RETURN_SEMA_FUNC_ERROR(callee->definition, call, "Too many arguments were provided for the formatting string.");
+	}
 	return true;
 NO_MATCH_REF:
 	*no_match_ref = true;
diff --git a/src/compiler/symtab.c b/src/compiler/symtab.c
index ca0e1efa4..8f41d7f57 100644
--- a/src/compiler/symtab.c
+++ b/src/compiler/symtab.c
@@ -327,6 +327,7 @@ void symtab_init(uint32_t capacity)
 	attribute_list[ATTRIBUTE_EXPORT] = KW_DEF("@export");
 	attribute_list[ATTRIBUTE_EXTERN] = KW_DEF("@extern");
 	attribute_list[ATTRIBUTE_FINALIZER] = KW_DEF("@finalizer");
+	attribute_list[ATTRIBUTE_FORMAT] = KW_DEF("@format");
 	attribute_list[ATTRIBUTE_IF] = KW_DEF("@if");
 	attribute_list[ATTRIBUTE_INIT] = KW_DEF("@init");
 	attribute_list[ATTRIBUTE_INLINE] = KW_DEF("@inline");
diff --git a/test/src/test_suite_runner.c3 b/test/src/test_suite_runner.c3
index 23acb7167..fdff8f522 100644
--- a/test/src/test_suite_runner.c3
+++ b/test/src/test_suite_runner.c3
@@ -448,7 +448,7 @@ fn void test_file(Path file_path)
 	if (result != 0 && result != 1)
 	{
 		(void)io::copy_to(&&compilation.stdout(), &out);
-		io::printfn("FAILED - Error(%s): ", result, out);
+		io::printfn("FAILED - Error(%s): %s", result, out);
 		return;
 	}
 	if (!parse_result(out, settings)) return;
diff --git a/test/test_suite/attributes/format_attr.c3 b/test/test_suite/attributes/format_attr.c3
new file mode 100644
index 000000000..c08234c96
--- /dev/null
+++ b/test/test_suite/attributes/format_attr.c3
@@ -0,0 +1,19 @@
+
+fn void foo(int x) @format(1) // #error: The format '@format()'
+{}
+
+alias Foo = fn void(String format, args...) @format(0);
+
+fn usz? printfn(String format, args...) @format(1) // #error: The format string cannot
+{
+	return 0;
+}
+
+fn void foo2(int x) @format(0) // #error: '@format()' is only valid for a function
+{}
+
+fn void foo3(int x, args...) @format(0) // #error: The '@format()' format
+{}
+
+fn void foo4(String #x, args...) @format(0) // #error: '@format()' cannot be used with lazy arguments
+{}