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Squoosh: free alternative to Image compression / format conversion tools — online
Need to turn JPG/PNG into WebP/AVIF without uploading the original? Pick this one: free open source, fully local WASM encoding, 7 output formats to compare.
| Replaces | Image compression / format conversion tools |
|---|---|
| License | Apache-2.0 (commercial use OK) |
| Runs on | online |
| Chinese UI | no (English UI) |
| Where files go | On your device (not uploaded) |
| Cost | Fully free and open source |
| Hands-on test | 2026-11-04 · squoosh.app live build (2026-11 mirror) |
Hands-on test (2026-11-04, squoosh.app live build (2026-11 mirror))
- License: Squoosh is an Apache-2.0 licensed open-source image compression web app (GitHub GoogleChromeLabs/squoosh); this self-hosted build mirrors the official static build
- Local WASM encoding: compression runs in browser Workers + WASM and images are never uploaded; the hands-on test loaded mozjpeg_enc / webp_enc / avif_enc / jxl_enc / squoosh_oxipng encoders
- Format coverage: AVIF, WebP, JPEG XL (beta), MozJPEG, OxiPNG, QOI and WebP v2 — 7 outputs with quality and advanced settings
- Side-by-side compare: original and compressed output shown together with live size and reduction (test: 800×600 PNG 87.7 kB → MozJPEG 63.8 kB, −27%)
- Preprocessing panels: built-in Resize and Reduce palette before compressing
Self-hosted hands-on test 2026-11-04: tools.cosmocat.dev/squoosh/ is live; a 25MB full static mirror (all codec wasm and workers) with paths rewritten to the /squoosh/ prefix; uploads and produces compressed output at 1280px and 390px with 0 errors and 0 missing assets
Best for
- Compressing JPG/PNG to WebP/AVIF
- Comparing size across encoders and quality levels
- Single-image tuning and format conversion before publishing
Not for
- Batch processing large image sets (use the Squoosh CLI or a script)
- SVG compression (use SVGOMG)
Similar alternatives
SVGOMGPhotopeaGIMP
How to get started
- Click "Use online" above — it runs in your browser, no signup required.
- Run the full workflow (open → edit → export) on a throwaway file first, to confirm format compatibility.
- Once you accept its limits, migrate your daily workflow; keep the original software as a fallback for critical deliverables.