Read the header of any JPEG XL file - lossless or lossy, bit depth, HDR, colour encoding, animation, extra channels and whether the original JPEG can be restored bit for bit. Need a PNG? Use JXL to PNG.
Want to make JPEG XL files? PNG to JXL and JPG to JXL run in your browser.
| Mode | How to tell | Used for |
|---|---|---|
| Modular, no XYB | xyb_encoded = false | Lossless images, graphics |
| VarDCT + XYB | xyb_encoded = true | Lossy photos |
| JPEG recompression | jbrd box present | JPGs shrunk about 20% with zero loss |
A JXL made from a JPG can be turned back into the identical JPG. The analyzer tells you when that reconstruction data is inside.
Safari 17+ and macOS / iOS apps open JPEG XL.
Chrome, Edge and Firefox do not show it by default yet - this page brings its own decoder, so the preview works in every browser.
To share a JXL anywhere, convert it with JXL to JPG or JXL to PNG. Animated? JXL to GIF.
Look at the Compression line. Modular coding without XYB is lossless; VarDCT with XYB is lossy. A JPEG reconstruction box means the original JPG can be restored exactly.
Yes. Chrome, Edge and Firefox cannot draw JPEG XL themselves, so the page decodes it with its own WebAssembly decoder - nothing is uploaded.
Yes. Animation timing, frame count and loops are read from the header and frames.
Yes - the transfer function (PQ, HLG, linear), primaries, white point, peak brightness and float bit depth.
No. The JXL is read in your browser and never leaves your device.
