The Magic of WebAssembly Codecs in the Browser
How compiling C/C++ image libraries to WASM makes serverless, high-fidelity compression possible.
SJ
Sarah Jenkins
Contributing Author · Squoosh Next BlogBefore WebAssembly (WASM), web-based image compression was limited to native browser Canvas APIs, offering only rudimentary control. By compiling high-performance native libraries such as libjpeg-turbo, libwebp, and libheif to WASM, developers can now run those identical algorithms directly inside the browser sandbox. This enables client-side apps to execute complex operations including trellis quantization, Lanczos resampling, and progressive scan encoding without any server processing.
The result is zero backend maintenance costs, absolute privacy since the image data never traverses a network, and performance characteristics within 10–15% of native execution speed in V8 and SpiderMonkey. Squoosh Next ships MozJPEG, OxiPNG, libwebp, and libaom as WASM modules loaded on demand.
Key Takeaways
Before WebAssembly (WASM), web-based image compression was limited to native browser Canvas APIs, offering only rudimentary control.
By compiling high-performance native libraries such as libjpeg-turbo, libwebp, and libheif to WASM, developers can now run those identical algorithms directly inside the browser sandbox.
This enables client-side apps to execute complex operations including trellis quantization, Lanczos resampling, and progressive scan encoding without any server processing.
The result is zero backend maintenance costs, absolute privacy since the image data never traverses a network, and performance characteristics within 10–15% of native execution speed in V8 and SpiderMonkey.
Try It in the Workspace
Everything discussed in this article can be tested directly in Squoosh Next — no sign-up, no upload, 100% client-side.