String builtins (WebAssembly)Limited availability

The WebAssembly builtin string functions mirror a subset of the JavaScript String API and adapt it to be efficiently callable without JavaScript glue code.

Not yet supported in all major browsers — check the table and provide a fallback.

How to use ↓Compare browsers

Browser support

DesktopChrome

1–129Not supported

130+Supportedsince Oct 15, 2024

Current: 155

Edge

12–129Not supported

130+Supportedsince Oct 17, 2024

Current: 154

Firefox

1–133Not supported

134+Supportedsince Jan 7, 2025

Current: 157

Safari

✕Not supportedup to 27

Current: 27

MobileChrome Android

18–129Not supported

130+Supportedsince Oct 15, 2024

Current: 155

Firefox Android

4–133Not supported

134+Supportedsince Jan 7, 2025

Current: 157

Safari iOS

✕Not supportedup to 27

Current: 27

How to use

Not supported in Safari, Safari iOS. Use feature detection below and provide a fallback (or a polyfill) for those browsers.

Example

Full syntax and examples are on MDN — see the links below.

Feature detection

There’s no simple runtime check for this feature; rely on the support table and test in your target browsers.

Specification

github.com/WebAssembly/js-string-builtins/blob/main/proposals/js-string-builtins/Overview.md ↗

Sub-features

Support for each part of the feature (7). The overall table above shows when the whole feature works.

Sub-feature	Chrome	Edge	Firefox	Safari	Chrome Android	Firefox Android	Safari iOS
webassembly.api.Module.Module.compile_options	130	130	134	✕	130	134	✕
webassembly.api.compileStreaming_static.compile_options	130	130	134	✕	130	134	✕
webassembly.api.compile_static.compile_options	130	130	134	✕	130	134	✕
webassembly.api.instantiateStreaming_static.compile_options	130	130	134	✕	130	134	✕
webassembly.api.instantiate_static.compile_options	130	130	134	✕	130	134	✕
webassembly.api.validate_static.compile_options	130	130	134	✕	130	134	✕
webassembly.jsStringBuiltins	130	130	134	26.2	130	134	26.2