GoKawiilSwift 6.4 ships with unified builds, stable Subprocess API, and faster WebAssembly
Apple's Swift language team has released Swift 6.4, which makes Swift Build the default engine in Swift Package Manager so projects compile identically on Linux, macOS, and Windows. The update also finalizes the Subprocess API at version 1.0 for cross-platform process management, expands C++ and Java interoperability, and speeds up WebAssembly execution via JavaScriptKit by up to 40 times.
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Standardizing the build system across operating systems removes a long-standing pain point for teams shipping cross-platform Swift code, while the Subprocess milestone gives developers a reliable, official way to shell out to other programs instead of relying on fragmented third-party solutions. The WebAssembly speedup and expanded Embedded Swift support also signal Apple's push to make Swift viable well beyond Apple platforms, from browsers to microcontrollers.
- Swift Build becomes the default in Swift Package Manager for consistent cross-platform compilation.
- Subprocess API reaches 1.0, offering a stable way to run external programs from Swift.
- WebAssembly performance via JavaScriptKit improves by up to 40x, with a new Wasm SDK on Swift.org.
Source: swift.org — Apple Inc., 2026-09-15
Published there as: “Swift 6.4 Released”
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