Swift 6.3: What to Expect in Spring 2026

The Swift 6.3 branch cut happened on November 12, 2025. Destination: WWDC 2026. This version marks a major turning point for Swift as a truly multi-platform language. Embedded Swift exits experimental, Android becomes an official target, and new platforms join the family. Here's everything we know.

Swift 6.3 is not a release focused on the language itself. The foundations laid by Swift 6.0 (strict concurrency) and refined by 6.1/6.2 (approachable concurrency) are solid. This time, the Swift team focuses on expansion: making Swift a viable choice everywhere, from microcontrollers to servers, including Android and the browser.

The three major axes of this release:

Introduced in preview with Swift 6.0, Embedded Swift allows writing code for microcontrollers and constrained environments. Swift 6.3 finalizes this feature with significant improvements.

Until now, displaying floating-point numbers required C dependencies. Swift 6.3 implements this feature in pure Swift, eliminating one of the last external dependencies.

The @c attribute (SE-0495) allows exporting Swift functions with a C-compatible ABI, facilitating integration with existing code. The syntax uses a standard Swift identifier, not a string.

These functions can be called directly from C code:

The new @section and @used attributes provide fine control over memory placement and symbol preservation.

The new Swift MMIO package simplifies access to hardware registers with code generation from SVD (System View Description) files. Properties use @RegisterBlock(offset:) with the Register<T> type wrapper.

Debugging on embedded targets finally becomes practical with an adapted LLDB: breakpoints, variable inspection, and stepping work on bare-metal ARM and RISC-V targets.

Announced in preview in October 2025, the Swift SDK for Android takes a step forward with Swift 6.3. Nightly builds are already available and documentation is expanding.

Swift compiles to native machine code for Android, exactly like for iOS. Performance is comparable to C/C++ code compiled with the Android NDK.

Note: The syntax below is illustrative. Currently, Android SDKs are installed via swift sdk install <URL>. Simplified swiftly integration is under development.

Most Android APIs are exposed via Java/Kotlin. The swift-java project provides the necessary tools.

Note: The example below represents a future vision of native Swift/Android interoperability. AndroidKit doesn't exist yet in official repos. Currently, Swift on Android uses JavaKit with JNI for business logic, with UI remaining in Kotlin/Java.

The most pragmatic approach today is to share business logic in Swift between iOS and Android, with native UIs on each platform.

The Skip framework offers an alternative approach: Swift → Kotlin transpilation and SwiftUI → Jetpack Compose for truly cross-platform apps.

Swift 6.3 brings preview support for FreeBSD 14.3 and later versions. A talk is scheduled at FOSDEM 2026 to present the port.

WebAssembly support introduced in Swift 6.2 continues to mature. Swift can now run in the browser or on WASI runtimes.

Experiments are underway to deploy Swift on Cloudflare Workers and Fastly Compute.

Windows support progresses with a more complete VS Code extension and a growing number of packages compatible out-of-the-box.

Some features are under discussion but not confirmed for Swift 6.3:

The community is asking for simpler macros to implement. Proposals are under review but nothing is guaranteed for 6.3.

Each release brings its share of improvements to Foundation. Swift 6.3 should continue on this path with new cross-platform APIs.

The Swift team continuously works on compilation times. Gains are expected, especially for projects using many macros.

Nightly builds are available for adventurous developers.

Note: Illustrative syntax. Currently, use swift sdk install <URL> to install Android SDKs.

Nightly builds are unstable by definition. Use them to explore and test, not for production. Some features may change before the final release.

Based on previous releases, here's what we can anticipate:

Swift 6.3 confirms Apple's vision: Swift is no longer just the language for iOS apps. It's a modern, safe, and truly portable systems programming language.