# externalMacro(module:type:) Specifies the module and type name for a macro’s implementation. ``` @freestanding(expression) macro externalMacro(module: String, type: String) -> T ``` ## Parameters `module` The module name. `type` The type that implements the macro. ## Return Value The macro’s implementation. ## Overview This macro can only be used to define a macro; using it in any other context is an error. The specified type must conform to the protocols that correspond to the roles of the macro being declared. For example: ```swift macro stringify(_ value: T) -> (T, String) = #externalMacro(module: "ExampleMacros", type: "StringifyMacro") ``` --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)