How img.lu works

img.lu converts and compresses your images to WebP entirely inside your browser. No file ever leaves your device. There is no server, no upload, no account — just your browser doing the work.

The technology

Your browser is more powerful than you think. Modern browsers ship a native API called the Canvas API combined with OffscreenCanvas and Web Workers, which allows JavaScript to read, decode, re-encode, and compress images without any network request.

img.lu uses the open-source browser-image-compression library on top of these APIs to:

1. Decode your source image (JPEG, PNG, GIF, HEIC, AVIF…)
2. Optionally resize it to a maximum dimension (default: 1600 px)
3. Re-encode it as WebP at your chosen quality level
4. Hand the result back to you as a download

All of this happens in a Web Worker thread — so your tab stays responsive even while compressing large batches.

What is WebP?

WebP is an image format developed by Google and now supported by every modern browser. It achieves:

WebP uses a combination of lossy and lossless compression, and supports transparency (like PNG) and animation (like GIF) in a single format.

Quality levels explained

img.lu offers three quality presets, which control the initialQuality parameter passed to the encoder:

• High Quality · 0.8 — Nearly indistinguishable from the original. Best for product photography or images that will be printed or zoomed.
• Balanced · 0.6 — The sweet spot for web use. Roughly 60–70% smaller than the original with no visible quality loss at normal viewing sizes.
• Extreme · 0.3 — Aggressively compressed. Ideal for thumbnails, previews, or any image that doesn't need to survive close inspection.

Your privacy

img.lu is built on a simple promise: your images never leave your device.

• No files are uploaded to any server
• No analytics capture your image names or dimensions
• No cookies track your activity beyond this session
• The only third-party request is Simple Analytics — a privacy-first, GDPR-compliant counter that records only a page view, with no fingerprinting and no personal data

img.lu is built and hosted in Luxembourg, under EU jurisdiction and full GDPR compliance.

Comparing before and after

Every compressed image card lets you hover to toggle between the compressed result and the original. The percentage badge shows exactly how much smaller the new file is. If the result doesn't look right, choose a higher quality level and re-drop the file — no page reload needed.

Downloading your files

Each card has its own Download button. If you've compressed several images, use Download All (.zip) to get a single ZIP archive containing every WebP file, ready to deploy.

Browser support

WebP encoding via the Canvas API works in every browser released since 2020:

• Chrome / Edge 79+
• Firefox 96+
• Safari 14+
• iOS Safari 14+
• Samsung Internet 12+

If you're on an older browser, the compressor will silently fall back to JPEG output instead of WebP.