Swift for Wasm April 2026 Updates

Max_Desiatov · April 30, 2026, 3:29pm

Notable changes this month: Wasm-compatible swift-tar library, JavaScriptKit 0.50.0–0.51 releases with continued BridgeJS work and a new opt-in pointer-identity mode for SwiftHeapObject wrappers, WasmKit updates unifying WasmKitError typed throws and removing any GuestMemory existentials from *Guest*Pointer types (plus a small 0.2.2 patch release), and ElementaryUI 0.2.0–0.2.2 focused on performance and stability fixes.

Many thanks to 0xpablo, @inductor, @kateinoigakukun, Ken Tominaga, @krodak, Matthew Ayers, @owenv, @sliemeobn, @wfltaylor, and @xavgru for contributions!

Forum Discussions

Swift-tar: A pure Swift TAR archive read/write/extract library — Foundation-free TAR library by @kateinoigakukun with WebAssembly and Embedded Swift support.

Swift Toolchain

Add integration tests for cross-compiling to WebAssembly swift-package-manager#9877;
build-script: rename WasmStdlib -> WASIStdlib swift#88469;
Docs: adjust WASI stdlib test execution command swift#88580;
Fix KeyPath with 16-byte-aligned subscript traps on 32-bit targets swift#88725;
lib/Basic: Emscripten triple support in swift-frontend swift#88732;
Add integration test for the WebAssembly Embedded Swift SDK swift-build#1154;
Fix test target compilation for WebAssembly swift-build#1348.

JavaScriptKit

Four releases this month: 0.50.0 introducing JSRemote<JSObject>, then 0.50.1, 0.50.2 bundling several BridgeJS fixes, finally 0.51.0 with identity mode, support for use of @JS types from other modules, simplified contributor setup, and few BridgeJS fixes.

Add JSRemote<JSObject> #711;
BridgeJS: fix for-loop emission in stack codegen #716;
BridgeJS: emit static methods and properties on namespaced class entries #717;
BridgeJS: fix code generation for public enums #719;
Import Android module for non-Wasm Android targets #722;
Adopt FoundationEssentials in compat module #725;
Add opt-in pointer-identity mode for SwiftHeapObject wrappers #723;
Add Utilities/setup-dev.sh for one-command contributor setup #726;
GC lifecycle test for identity-cached wrappers #731;
BridgeJS: Use @JS types from other modules in the same package #730
BridgeJS: Synthesize typed-closure init access from declaration surface #727.

WasmKit

Version 0.2.2 released, a small patch fixing subscript visibility. Meanwhile, on the main branch we saw portability and performance improvements.

Use unified WasmKitError for typed throws #277;
Remove any GuestMemory existential from *Guest*Pointer types #339;
Fix subscript visibility #341;
Fix fd handling in WASIp1 implementation #327.

ElementaryUI

Three releases this month (0.2.0, 0.2.1, 0.2.2). The focus was performance work and stability fixes.

Upgrade to JavaScriptKit 0.50 #92;
Noncopyable node types #94;
Reusable move-only scratch containers #91;
Minor performance tweaks #93;
Improved string handling #95;
Improved conditional mounting (fixes access-violation bug) #97;
Fix stale state tracking (optional-unwrap crash) #100.

Other Notable Changes

Add multi-version matrix support to Wasm Swift SDK workflow apple/swift-nio#3575.

Thank you for reading, and please feel free to add any comments or suggestions if we missed anything!

If you'd like to catch up with changes from previous months, here's a list of relevant updates: