How it works
The image is redrawn on an HTML5 canvas and re-exported at the chosen quality level, all locally in your browser. Lower quality means a smaller file — but also lower visual fidelity, so it's worth testing a few values to find the right balance.
Why PNG sometimes barely shrinks
PNG is a lossless format: the quality control has no effect on it the way it does on JPG/WEBP. If your image is a PNG and you want real size reduction, switch the output format to JPEG or WEBP (JPEG loses transparency).
Frequently asked questions
Is my image uploaded to a server?
No — compression happens entirely in your browser using the Canvas API. Your image never leaves your computer.
Why didn't the compressed image get much smaller?
If you kept the PNG format (lossless), the reduction is usually small. For bigger reductions, switch to JPEG or WEBP and adjust quality.
Is there a size limit?
Yes, the limit is 20MB per image.