Reference
Image formats, explained
Ten formats, what each one is genuinely good at, and what you give up moving between them. No format is best; they were designed for different problems.
Every format Lean Image reads
- JPEGread and writeThe lossy photo format every device on earth can open, essentially unchanged since 1992.
- PNGread and writeLossless, universally supported, and the safe answer whenever transparency or exact pixels matter.
- WebPread and writeGoogle’s replacement for both JPEG and PNG — smaller than either, and supported by every current browser.
- AVIFread and writeThe smallest files of anything here at a given quality, at the cost of the slowest encode and the newest support.
- GIFread and writeCapped at 256 colours per frame, which is why it is wrong for photographs and right for almost nothing else in 2026.
- BMPread onlyWindows’ uncompressed bitmap — every pixel stored literally, which is why a modest photo runs to tens of megabytes.
- SVGread onlyNot an image but a drawing instruction — resolution-independent, and the only format here you can open in a text editor.
- HEICread onlyApple’s default camera format since iOS 11 — around half the size of JPEG, and unreadable on a stock Windows install.
- JPEG XLread onlyTechnically the strongest format in this list and the least supported — Safari shows it, most other software still does not.
- TIFFread onlyThe scanning and print archive format — high bit depth, many pages per file, and no browser will display one.
Convert something
Pick a format above, or drop a file into the optimizer and choose as you go.