Swift 6.4: one build system for Mac, Windows, Linux, and Android

The release of Swift 6.4 makes Swift Build — Apple’s own build tool — the default in Swift Package Manager for the first time, giving developers a single command that compiles the same code on macOS, Linux, Windows, and now Android. For anyone who builds mobile or desktop software, the change eliminates a source of friction that had persisted since Swift went open source in 2015.

Android support arrives through the Android NDK 30 toolchain, a pairing that positions Swift as the first Apple-originated language with official cross-platform reach that includes Google’s mobile ecosystem. Projects can now share business logic, networking code, and data models across iOS and Android using one Swift package — instead of rewriting the same logic in Kotlin.

The release compounds the Android news with two performance jumps. The JavaScript bridge for WebAssembly runs 40 times faster than in Swift 6.3, reducing the lag that made SwiftWasm-based web apps feel slow compared to Rust or C++ equivalents. Subprocess 1.0 also ships stable in this release, providing a structured API for launching and communicating with external processes — a long-requested tool for server-side and command-line Swift programs.

Two language-level additions round out the release. Async defer blocks let functions clean up resources asynchronously when control leaves a scope, a pattern previously available only through synchronous defer or manual continuation. UniqueArray, a new collection type, enforces element uniqueness at the type level rather than at runtime, catching a class of logic bugs that had previously required manual deduplication.

The C++20 std::span bridge extends an ongoing effort to make C++ interoperability production-ready. Combined with the expanded Java and Kotlin call bridge from Swift 6.3, the new release makes a clear case that the language has outgrown its reputation as Apple’s in-house toolchain and is now a contender as a general-purpose cross-platform systems language.

Tags: Apple, programming, Android, open-source, Swift, Swift Package Manager