How image compression works
- JPG and WebP use lossy compression: fine detail that the eye barely notices is removed. A quality setting of 70–80% usually halves the file size with no visible change.
- PNG files are reduced by limiting the image to a palette of up to 256 colors, the same approach used by popular PNG optimisers. This suits logos, screenshots and illustrations. Photos saved as PNG are better converted to JPG or WebP.
If compression would not make a file smaller, the original is kept, so a file never grows.
Why smaller images matter
Images are usually the heaviest part of a web page. Smaller files load faster, use less mobile data and improve Core Web Vitals scores, which Google uses as a ranking signal. They are also easier to email and upload to forms with size limits.
Recommended settings
- Website photos: quality 70–80%, maximum width 1600–2000 px, WebP if your site supports it.
- Email attachments: quality 60–70%, maximum width 1200 px.
Private by design
The image is opened and processed by your browser on your own device. It is not uploaded to a server, so the tool also works offline once the page has loaded.