How it works
Your browser decodes each image, draws it on an invisible canvas and saves it again in the format you choose. The work happens in a background thread, so the page stays responsive even with large photos. Images are converted one at a time to keep memory use low on phones.
Images up to 50 MB are accepted. Pictures larger than 16.7 megapixels (4096 × 4096) are scaled down to that size, because that is the largest image some browsers, including Safari on iPhone, can process. The result tells you when this happens.
Which format should I use?
| Format | Best for | Transparency | Compression |
|---|---|---|---|
| JPG | Photos, sharing, email, compatibility with everything | No | Lossy: small files, some detail lost |
| PNG | Screenshots, logos, text, graphics with flat colours | Yes | Lossless: exact pixels, larger files |
| WebP | Websites and apps | Yes | Lossy here: usually smaller than JPG at similar quality |
Google’s own measurements found lossy WebP files 25–34% smaller than JPG files of comparable quality. All current browsers display WebP, but some older desktop software cannot open it; convert to JPG when in doubt.
Quality setting
For JPG and WebP, the quality slider trades file size against detail:
- 90–100%: visually identical to the original, large files.
- 75–85%: the usual choice for photos on the web; differences are hard to see.
- Below 60%: noticeably blurry or blocky, especially around text and edges.
PNG is always lossless, so it has no quality setting. Converting a photo to PNG usually makes it much larger without improving it; PNG only helps with graphics, screenshots or when you need transparency.