Compress Images · JPG, PNG & WebP
Lossless, near-lossless or lossy — real codecs (MozJPEG, libwebp, OxiPNG) running entirely in your browser.
How to compress an image online (free)
- Drop your images onto the box above, or click to choose them.
- Pick a compression level (lossless, near-lossless or lossy) and an output format. In lossy mode, drag the Quality slider or set a target size in KB.
- Click Compress, then download each result or use Download all.
Lossless vs. near-lossless vs. lossy
Lossless keeps every pixel exactly as it was and still shrinks the file by re-packing it more efficiently — for PNG this uses OxiPNG, and WebP has a true lossless mode. It's the right choice for screenshots, logos and line art. Near-lossless (glossy) allows tiny, usually invisible changes for a much smaller file. Lossy trades visible detail for the smallest possible file and is controlled by the quality slider — ideal for photographs.
Real codecs, not just the browser
Unlike tools that rely on the browser's built-in canvas encoder, this compressor ships MozJPEG, libwebp and OxiPNG compiled to WebAssembly. That means smaller files at the same visual quality, plus lossless and near-lossless modes the browser can't produce on its own — all still running locally on your device.
Quality slider vs. target size
In lossy mode the quality slider gives you direct control — lower quality means smaller files. Target size is easier when you have a hard limit (say a 200 KB upload cap): the tool re-encodes the image a few times to find the highest quality that still fits under your number. If you set a target size it takes priority over the slider.
Which format compresses best?
WebP almost always produces the smallest file at a given quality, supports transparency, and offers lossless and near-lossless modes, so it's the default here. JPG is the safest choice for maximum compatibility with older software (note that JPEG has no true lossless mode — the lossless option encodes it at top quality). PNG stays lossless with OxiPNG, or is palette-reduced in lossy mode. Keep original re-encodes each image in its own format.
Why katlab's image compressor is different
Most "compress image" sites upload your pictures to their servers. This one doesn't. The compression happens inside your browser tab using WebAssembly codecs, so your images never touch the network — nothing to leak, cache, or delete later.
Is it really private?
Yes. There is no upload step and no account. You can open your browser's network tab and watch: no request carries your image data. The tool works offline once the page has loaded.
Will compressing reduce quality?
Only if you want it to. Lossless mode preserves quality exactly; lossy and near-lossless trade some detail for a smaller file. Keep your originals if you might need full quality later, since lossy compression cannot be undone.