WebAssembly
Use WebAssembly in your extension without custom bundler setup.
Extension.js ships with built-in WebAssembly defaults in its Rspack pipeline, so common wasm workflows work out of the box.
When WebAssembly is a good fit
- Your extension runs compute-heavy tasks (parsing, media, OCR, transforms).
- You need near-native performance for hot code paths.
- You are reusing existing wasm modules from web projects.
WebAssembly capabilities
| Capability | What it gives you |
|---|---|
| Built-in wasm pipeline defaults | Run common wasm flows without manual bundler wiring |
| Async wasm support | Load .wasm modules in extension contexts |
| Runtime compatibility helpers | Handle common wasm ecosystem asset patterns |
| Regular command workflow | Use wasm with the same dev and build commands |
What Extension.js enables
The wasm plugin configures:
experiments.asyncWebAssembly = true.wasmin module resolution extensions- runtime asset aliases for common wasm ecosystems (for example ffmpeg, imagemagick wasm, tesseract wasm)
This reduces boilerplate when importing wasm modules from extension scripts/pages.
How to use
Use wasm modules in your extension code as part of regular development/build flows:
You can also test against a known public sample:
Typical use cases
- compute-heavy parsing/transforms
- media processing pipelines
- OCR / image processing workflows
- performance-sensitive algorithms shared across web/runtime contexts
Best practices
- Keep wasm modules focused on hot paths; keep orchestration logic in JavaScript/TypeScript.
- Validate output size and load timing for extension contexts (background, content scripts, pages).
- Test wasm-heavy flows across browser targets you ship (
chrome,edge,firefox).
Next steps
- Learn more about WebAssembly.
- Learn how Extension.js works with ECMAScript Modules.
ON THIS PAGE