Browser WASM API

@imagemin-rs/wasm runs the shared imagemin-rs Rust pipeline in browsers and Web Workers. It is asynchronous and memory-only: inputs and outputs are Uint8Array values, with no Node.js native binding or executable sidecar.

For a complete file-input, module Worker, cancellation, download, and deployment walkthrough, start with the Browser and Web Worker Guide.

Install and initialize

pnpm add @imagemin-rs/wasm

Initialize once before calling a plugin or pipeline API. Normal browser ESM imports and bundlers load the adjacent .wasm asset automatically. An explicit URL, WebAssembly.Module, response, or byte buffer can be supplied when an application has its own asset policy.

import { initWasm, isWasmInitialized } from "@imagemin-rs/wasm";

await initWasm();
console.log(isWasmInitialized()); // true

Repeated calls share the same initialization promise, and a failed attempt can be retried.

Optimize in memory

import { initWasm, optimize, oxipng } from "@imagemin-rs/wasm";

await initWasm();

const input = new Uint8Array(await (await fetch("/image.png")).arrayBuffer());
const result = await optimize(input, {
  plugins: [oxipng({ optimizationLevel: 3, strip: "safe" })],
});

console.log(result.data, result.inputBytes, result.outputBytes, result.steps);

The supported built-in factories are:

Factory	Input	Behavior
oxipng()	PNG	Lossless Oxipng profile; never keeps a larger result.
optipng()	PNG	Native OptiPNG-compatible option mapping.
giflossless()	GIF	Frame-preserving lossless animation optimization.
svgm()	SVG	Bounded native SVG optimization with safe/default modes.

Adjacent built-in plugins are sent through one Rust pipeline call. Custom browser plugins remain ordinary functions and execute strictly in array order:

const copy = async (input: Uint8Array) => new Uint8Array(input);

const result = await optimize(input, {
  plugins: [oxipng(), copy],
});

Errors and cancellation

Rust validation and codec failures reject with ImageminError. Its code is a stable ERR_IMAGEMIN_* value and plugin identifies the active built-in profile when available. Initialization and asset-loading failures use ERR_IMAGEMIN_WASM_LOAD.

AbortSignal is checked between plugins. WebAssembly computation is synchronous once it starts, so a signal cannot preempt an active codec call. Run CPU-heavy work in a Web Worker and terminate that Worker when hard cancellation is required. The documentation Playground uses this model.

Runtime boundary

The package does not expose file paths, glob expansion, a destination directory, CLI commands, a disk cache, N-API, or executable sidecars. Consequently gifsicle, pngquant, mozjpeg, jpegtran, webp, and avif are Node-only. svgo also stays at the JavaScript compatibility seam; use svgm() for the shared Rust/WASM profile.

Packed-package acceptance runs in Chromium, Firefox, and WebKit. Applications must serve .wasm files with application/wasm for streaming compilation; the generated loader falls back to buffered instantiation when necessary.