Setting the Swift tools version

Define the minimum version of the swift compiler required for your package.

Overview

The tools version declares the minimum version of the Swift compiler required to use the package, as well as how parse the Package.swift manifest. When you create a new package using doc:PackageInit, the minimum version is set automatically to the current version. The version is specified on the first line of the manifest with the comment // swift-tools-version: and the version for the Swift compiler. The version is a semantic version, with the exception that a patch version is inferred to be 0 if you don't specify it.

For example, the following line asserts the package requires the Swift compiler version 6.1 or later:

// swift-tools-version:6.1

Resolving dependencies with different tools versions

When resolving package dependencies, if the tools version of a dependency is greater than the version in use, that version of the dependency is ineligible and dependency resolution continues with evaluating the next-best version.

If no tools version of a dependency, which otherwise meets the package version requirements, supports the version of the Swift tools in use, the package manager presents a dependency resolution error. For more information on providing package manifests for specific Swift versions, see doc:SwiftVersionSpecificPackaging.

Adjusting the tools version.

Edit the Package.swift to adjust the version, or use doc:PackageToolsVersion to report or set the the tools version.