Squoosh
FreeCompress images in a web page — with nothing uploaded
A web-based image compression and format conversion tool from Google Chrome Labs. A split view compares original and compressed quality in real time while you adjust quality, dimensions and encoder settings, with support for WebP, AVIF, JPEG XL and MozJPEG. **All processing happens locally in the browser — images are never uploaded.**
Why we picked it
Online image compressors are everywhere, and they share one problem: your images end up on someone else's servers. Product photos, design drafts, scanned documents, unreleased work — once uploaded, how long they are kept, who sees them and whether they feed a training set is unknowable.
Squoosh works differently: it is a web page, but all computation runs inside your browser, with the encoders compiled into the page as WebAssembly. Your image never leaves your computer — which you can verify yourself, since it keeps working with the network disconnected.
The most valuable part in practice is live comparison: a draggable divider down the middle with the original on one side and the compressed result on the other, quality adjustable by slider with the difference visible immediately and the resulting file size and percentage saved displayed below. You can find the precise point where further compression becomes visible, rather than guessing at 80%.
Encoder coverage is thorough:
- WebP: widely supported now, typically 25–35% smaller than JPEG.
- AVIF: higher compression again, smaller at equal quality, supported by modern browsers.
- JPEG XL: a next-generation format with excellent ratios, though browser support is still arriving.
- MozJPEG: an optimized JPEG encoder and the safest choice for compatibility.
- OxiPNG: lossless PNG compression.
It also resizes, reduces palette colors and applies dithering, which is practical for web assets and blog images.
To be clear about:
- It handles one image at a time. This is a precision tool, not a batch processor. For hundreds of files use ImageMagick on the command line, or Caesium.
- Large images consume memory, since everything runs in the browser; very large files can be slow or memory-hungry.
- Updates are infrequent. It is a Chrome Labs experiment whose functionality is mature and stable rather than a continuously iterating product. Being purely client-side, it keeps working regardless.
- It works offline. As a PWA it can be installed to your desktop after the first visit and opens without a connection — incidental proof that it genuinely needs no server.
For compressing an image before a blog post, a web page or a social share, this is both the easiest and the most trustworthy option.