How it works

ShrinkLocal is for people who need to compress large images (often 5MB, 10MB, or more) without sending files to a cloud service. You can process multiple files in parallel and download them individually or as a ZIP.

1. You choose or drop one or more images. Files stay on your device.
2. You pick an output format: JPEG (MozJPEG) or WebP.
3. Web Workers load encoders (WebAssembly) from this website — up to several images at once.
4. Each worker decodes your image, optionally scales very large dimensions, then encodes to your chosen format.
5. You download files one by one or as a ZIP archive. Nothing is stored on our servers.

Verify no upload (Chrome / Edge / Firefox)

1. Open ShrinkLocal.
2. Open Developer Tools → Network tab.
3. Enable Preserve log. Filter by Fetch/XHR (optional).
4. Compress one or more images.
5. Inspect requests: you should see loads for .js, .wasm, and HTML — not multi‑megabyte POST bodies of your photos.

Your image bytes are processed inside the browser. We have no API that accepts image uploads.

Output formats

JPEG (MozJPEG)

• Best for photos, email attachments, and tools that expect .jpg.
• PNG and WebP inputs with transparency are composited on a white background.

WebP

• Often smaller than JPEG at similar visual quality — ideal for websites and blogs.
• Transparency is preserved when the source PNG or WebP has an alpha channel.

For both formats: if either side exceeds 8192px, the image is scaled down proportionally first.

Batch & ZIP

• Up to 20 images per batch (configurable in our app).
• All files in one batch use the same output format you select before processing.
• Download all as ZIP bundles every successful result locally — still no server upload.

Recommended browsers

Latest Chrome, Edge, or Firefox on desktop. Large files (50MB+) need enough RAM; mobile may struggle with very large batches.

Technology

Encoders come from jSquash (MozJPEG and libwebp, same family as Google’s Squoosh). WASM modules are self-hosted on this domain.