What is the JXL file format?
A JXL file stores an image in JPEG XL, a general-purpose image format developed by the JPEG committee and published as the ISO/IEC 18181 standard. Its bitstream was frozen in January 2021, and the format is royalty-free. The reference encoder and decoder, libjxl, is open source and led by Google and Cloudinary.
One .jxl file can hold either lossy or mathematically lossless images, so a single format covers both photographs and flat graphics. It also supports alpha transparency, multi-frame animation, high dynamic range, and wide color gamuts up to 32-bit per channel. Compared with a .JPG at the same quality, a JPEG XL file is usually smaller, and it adds the transparency that JPEG never had.
A standout feature is lossless recompression of existing JPEGs: a regular JPEG can be repacked into JXL about 20% smaller and later restored to the exact original bytes. Most people meet the format when a website or image tool offers JPEG XL as an export option, or when they download a .jxl file and their usual viewer does not recognize it yet. Apple added native support in macOS 14 and iOS 17; on Windows and Linux you add support through an image viewer or the libjxl command-line tools. Its main rival is .AVIF, which uses the AV1 codec.
Security & safety
RISK: LOWA JXL file is passive image data and cannot run code on its own. As with any image format, keep your decoder or viewer updated, since parsing bugs in an image library are the only realistic risk vector.
Format details
in a nutshellPrograms that open JXL files
Windows4 apps
IrfanView (+ JPEG XL plugin)
Free Install the IrfanView plugins pack, then open the .jxl file normally. 
macOS2 apps
Preview
Built-in Double-click the .jxl file; Preview on macOS 14 Sonoma and later opens it natively. 
Linux3 apps
Photos / Files
Built-in Open the .jxl file in Files or Photos; iOS 17 and later supports it natively. Technical details
deep spec| Encoding | binary |
| Byte order | big-endian (ISOBMFF box headers); code-stream is bit-packed |
| Container | ISOBMFF box structure (optional) or a bare code-stream |
| Compression | JPEG XL (Modular mode for lossless, VarDCT for lossy); also losslessly recompresses existing JPEG data |
| Typical size | 40 KB - 20 MB |
| Structure | Signature box, then the JXL code-stream (one or more frames), plus optional Exif, XMP and ICC-profile boxes |
| Versioning | code-stream level 5 (default limits) or level 10 (extended limits) |
| Color depth | up to 32-bit floating point per channel; alpha, HDR and wide-gamut color |
| Dimensions Limit | up to 1,073,741,823 (2^30-1) pixels per side at level 10 |
| Platforms | Windows, macOS, Linux, iOS, Android |
| Initial Release Full | Code-stream frozen January 2021; ISO/IEC 18181-1:2022 |
| Notes | A defining feature is lossless, reversible transcoding of existing JPEG files, typically ~20% smaller. Native operating-system support arrived with macOS 14 Sonoma and iOS 17 (2023). Google removed the experimental JPEG XL flag from Chrome in version 110 (2023). |
| Released | 2021 (bitstream frozen January 2021; ISO/IEC 18181-1 published 2022) |
| Latest version | ISO/IEC 18181 parts 1-4 (2022-2024); reference libjxl 0.11 (2024) |
| Open standard | Yes · royalty-free |
| Specification | jpeg.org |
JXL conversions
Community Q&A
asked by usersNo questions yet - be the first to ask about JXL files.
Frequently asked questions
How do I open a JXL file?
Why won't my browser open a .jxl file?
Is JPEG XL better than JPEG?
Can I convert JXL to JPG?
djxl image.jxl image.jpg, ImageMagick or GIMP. If the JXL was created by losslessly transcoding a JPEG, the original JPEG can be recovered byte-for-byte.
