Swift 6.4 expands concurrency, Android and WebAssembly support
Swift’s latest release adds testing and tooling updates, promotes its Subprocess library to version 1.0 and extends interoperability across platforms.
Swift 6.4 is now available, with Swift.org positioning the release as an expansion of the language’s reach across apps, servers, systems code, embedded devices and browsers.
The update adds support for combining asynchronous calls in defer blocks, alongside cancellation shields designed to ensure cleanup work runs regardless of how a function returns. Foundation and standard-library changes also improve support for modern APIs and existing types.
Swift’s Subprocess library has reached version 1.0 after its initial 0.1 release in 2025. Built around Swift concurrency, the cross-platform package is designed to run and interact with subprocesses.
Testing changes are aimed at easing migration between Swift Testing and XCTest. Developers can use XCTAssert in Swift Testing tests and #expect within XCTest cases, repeat test cases with swift test, and record Transferable attachments on Apple platforms.
The release also extends Swift’s platform interoperability. Swift.org says JavaScriptKit’s safe WebAssembly bridging is up to 40 times faster than earlier dynamic bridging, while Foundation adds FileManager support on WASI.
On Android, Swift Build now supports the platform in Swift Package Manager, removing the need for a post-install script. The Swift SDK for Android uses the LTS NDK 30. Swift 6.4 also adds Embedded Swift improvements, documentation through Swift’s new documentation site and open-source standard-library documentation content.
