What it is

JPEG XL: still raster image or animated raster image with layers, transparency and meta data, MIME type is image/jxl
JPEG XL (file extension .jxl) is an industry standard file format, based on the proposals of Pik and FUIF (which is based on FLIF).

• Suitable for picture archiving while preserving quality (lossy and lossless modes available)
• File Exchange Format (mailing, web pages with fast progressive loading)
• Lossless transcoding of existing images to compress more efficiently, for older formats like JPEGs, GIFs, PNGs, lossless WebPs, TIFFs
• Applications which require cost-effective and energy-efficient encoding and decoding while preserving high-fidelity images
• Content Providers can optimize JXL images for either faster decoding or even smaller file sizes
• Browsers would be able to remove their JPEG decoder thus reducing maintenance, because the decoder for JPEG XL can decode JPEGs, too
• Content Delivery Networks would be happy not to use animated GIFs or (animated) PNGs for simple raster graphics anymore

JPEG XL has 3 major encoding paths while preserving meta-data and color profile:

• lossless re-encoding of traditional JPEGs (replacing huffman by brotli, gaining around 20%)
• Modular: lossless re-encoding of any raster graphic (including transparency and layers)
• VarDCT: lossy transcoding of any common image format (including transparency and layers)

Seamless transition and codec replacement for older formats:

• JPEG -> the huffman entropy encoding is replaced by brotli, thus gaining 18-22% smaller files
• animated GIF -> animated lossless JPEG XL can preserve all the details, even transparency
• PNG / animated PNG -> animated lossless JPEG XL can preserve all the details, even transparency
• lossless / lossy / animated WebP -> lossless JPEG XL will preserve all the details, even transparency - you could opt for lossy JXL
• AVIF -> you probably would transcode to lossy JPEG XL (transparency will be saved)
• HEIC -> you probably would transcode to lossy JPEG XL
• TIFF (JPEG encoded) -> JPEG XL can save around 20% of the filesize while preserving layers and transparency
• TIFF (deflate) -> lossless JPEG XL preserves the details and transparency - can use CMYK too

If pixel-perfect re-encoding is not the primary objective, JPEG XL can encode to much smaller files while maintaining perceived quality.

Check JXL support in your browser

Check to see if you can view a JXL image file:


Note: For Chromium and Firefox users, a possible route is to use a WASM (WebAssembly) module like jxl_dec.wasm for decoding (see jxl.js in table below).

JXL is supported by the following applications (and many more):

software	version	decode		encode
		image	metadata	encode
Gimp	2.10+	Works with preliminary plugin from JPEG-XL repository.		Works with preliminary plugin from JPEG-XL repository. With extra options for encoding (encoding speed, distance, ...) Saving to JPEG-XL in Gimp plugin only available when reference software is compiled with option -DJPEGXL_ENABLE_GIMP_SAVING=1
djxl	0.11.1	JPEG-XL Reference Software command line tool Usage: djxl input output Tool is included in Debian “bookworm” package: libjxl-tools
cjxl	0.11.1			JPEG-XL Reference Software command line tool Usage: cjxl input output Get more options with: # cjxl -v -v -h Tool is included in Debian bookworm package: libjxl-tools
jxlinfo	0.11.1		JPEG-XL Reference Software example tool Usage: jxlinfo [jxl file]
KDE/Qt applications		yes, with qt-jpegxl-image-plugin		yes, with qt-jpegxl-image-plugin
exiftool	12.23+		yes, recognizes both: codestream-only format JXL container with XMP/EXIF data
ImageMagick	7.0.10-54
gThumb	3.11.3	display	yes
https://squoosh.app a WASM app for browsers uses libjxl v0.3.1		in-browser WASM / JS JPEG-XL decoding		JPEG-XL encoding multiple options w/ effort slider
https://github.com/niutech/jxl.js a WASM (WebAssembly) module for browsers uses libjxl v0.3.1	available since 2022-11-15	in-browser-app WASM / JS JPEG-XL decoding Import JXL support in a webpage with a few JS files and a WASM file. Works with: img tag picture / srcset tag css background url the WebAssembly module jxl_dec.wasm is from the Squoosh app	width and height are retained	-
Safari Browser	iOS / macOS 17+	supported on macOS and iOS devices from version 17 onwards (2023 release) since 2023-09-18
GNOME Web code name: Epiphany Browser	45	supported via WebKitGTK rendering engine
DNG file format	1.7+ since 2023/06	efficient compression of RAW and lossy image data	yes	yes
DICOM data format	2024d since 2024/09	efficient compression lossy, lossless, or JPEG re-encoded image data	yes	yes
discontinued products
Mozilla Firefox Browser	Nightly 90+ only	In Firefox version 90+ Nightly builds only: Go to about:config toggle image.jxl.enabled to switch it on The builds have integrated a recent version of the libjxl library, updates of libjxl will be applied to Firefox Nightly every few weeks. Missing in Firefox decoding JXL partial decoding of progressively encoded JXL images is unsupported yet animations not running yet alpha channel isn’t properly filtered Patches for color profiles, progressive decoding and animated JXL decoding already on hand since August 2021 but not merged into application yet. New on Sep 4 2024: Firefox says it will consider a Rust implementation of JPEG-XL. https://github.com/mozilla/standards-positions/pull/1064
Chrome Browser Desktop only,development halted.	91-109 only	Note: Format integration/support halted. JPEG-XL Go to chrome://flags toggle enable-jxl to switch it on Chrome had a relatively fast JXL decoder behind a flag, but no future plans for this format at the moment.

Main Features

lossless re-encoding from JPEG-old-style and PNG.
It supports bitdepths from 1-32 bits/channel, progressive encoding/decoding, lossless encoding, transparency, speed vs. compression presets, chroma subsampling, further “extra” channels for e.g. depth information, UV or (thermal) infrared.
Available mode for putting center groups first in the stream to decode a file from the middle out.
Furthermore, there is support for HDR, layers, animation and multithreaded/SIMD-optimized decoding.
Is generally superior to: WebP, HEIC and AVIF in terms of image quality and fidelity.

Allowed entropy coders

• Brotli
• ANS (Asymmetric Numeral System)
• sANS
• Binary arithmetic coding (BAC)
• Histogram code (i.e., Huffman)
• ABRAC (Adaptive binary range coding)

Installation of the reference software

Along with the library, you get encoding and decoding tools for the JPEG-XL image format.

Build from source:

Go to:
https://github.com/libjxl/libjxl
or
https://gitlab.com/wg1/jpeg-xl
to check the guide there.

Download step is:
via github:
git clone --depth 1 https://github.com/libjxl/libjxl.git --recursive
via gitlab (this project is just a mirror of the one at github):
git clone https://gitlab.com/wg1/jpeg-xl.git --recursive
Then build according to the README.md
Make and install the package.

The tools for encoding/decoding are called cjxl and djxl. Example tool jxlinfo gives codestream meta information.

Browser Support

This code snippet should work if you have one of these conditions met:

• If you had a working browser for that, like Firefox Nightly version 90+, GNOME Web 45+, Pale Moon, or Safari 17+, maybe an old Chromium version 91-109, or
• the jxl_dec.wasm WASM (WebAssembly) module to decode <img> or <picture> tags or css background images which are provided as JXL file format.

A working code example to display a JXL picture would be then:

Gimp Plugin

Gimp has JPEG-XL included since 2.10.32. The mimetype is image/jxl, the file extension is .jxl

This paragraph explains installation of the JXL plugin in Gimp versions prior to 2.10.32.
Note: with package libgimp2.0-dev installed beforehand, you can also create the JPEG-XL load/save plugin for Gimp with this source package.
When configuring the libjxl git clone before build, use these additional flags to create the Gimp plugin: -DJPEGXL_ENABLE_PLUGINS=ON -DJPEGXL_ENABLE_GIMP_SAVING=1

Claws-Mail Plugin

In Debian Bookworm, JXL isn’t readily available in most applications.
For instance, to make claws-mail recognize the new file format, there has to be file libpixbufloader-jxl.so in the corresponding gdk-pixbuf-2.0 plugin directory.
To make claws-mail aware of that new type, it might be necessary to add a new paragraph with additional lines in loaders.cache, like this example for arm64 machines:

"/usr/lib/aarch64-linux-gnu/gdk-pixbuf-2.0/2.10.0/loaders/libpixbufloader-jxl.so"
"jxl" 4 "gdk-pixbuf" "JPEG XL image" "BSD-3"
"image/jxl" ""
"jxl" ""
"\377\n" "  " 100
"...\fJXL \r\n\207\n" "zzz         " 100

Installation from distribution (official package):

All distributions
Package name is libjxl.

Debian
Debian package names for JXL libraries/utilities are: jpeg-xl-doc, libjxl-dev, libjxl-tools, libjxl0.7, libjxl0.8, libjxl0.9 (see https://packages.debian.org/bookworm/libjxl0.7)

If you have an up-to-date stable release installed, there are at least two ways to install packages of the recent “bookworm” suite:

• Use the “bookworm” repositories to get some basic support and header files, or:
• You can still (cross-)compile the tools from source to even get the plugins for gdk-pixbuf JXL support, see section above where to get the files.

 

Encoding and Decoding on the Linux Command Line

These tools are provided by the reference software.
cjxl - Encoding input image to JPEG-XL format, is capable of losslessly re-packing JPEG-1 images, including metadata
djxl - Decoding JPEG-XL to older image formats
jxlinfo - gives meta information of a JPEG-XL file

KDE/Qt support based on libjxl

Basic JXL support is included in recent versions.
In Debian, this has been released with “bookworm” in 2023.

Qt support for older installations: manual installation of plugins

(e.g., for image viewers like Gwenview):
Go to: https://github.com/novomesk/qt-jpegxl-image-plugin to check the guide there.

Basically, these are the steps for installation:

Fetch and install the reference software, see section “Installation of the reference software” above. Update mime database file

Make sure you have the Qt5 base development files installed. Correct package name for Debian/Ubuntu is: qtbase5-dev
Then, download the plugin: git clone --depth 1 https://github.com/novomesk/qt-jpegxl-image-plugin

JPEG-XL - File header structure

JXL files can be stored with or without a container.
The container can create more complex files.
Without a container, there are only 2 signature bytes FF 0A and frame data.

with container structure (e.g., to include an Exif header):
Magic bytes

When a container is used for a JXL file, the box signature before the actual frame data is ‘jxlc’ (6a 78 6c 63)

Low-level frame data,
without the container (might be at the start or inside, at a later position in file):
Magic bytes

following: frame metadata, codestream data (entropy encoded)


Sample JPEG-XL begin with container boxes
and file signature (magic bytes in orange)

Possible JXL container boxes are
Exif, jxlc, jbrd, xml  (used for XMP), jumb (JUMPF), brob (Brotli-compressed box containing metadata like Exif, xml , ...), jxli, jxlp, ...

JXL container box format

length (4 bytes, little-endian)

box type (4 bytes, 4-letter name, like ‘Exif’)

raw content

Proposal: JPEG-XL as more efficiently raster image codec in next-gen PDF documents

https://www.reddit.com/r/jpegxl/comments/zwc5ro/is_it_possible_to_use_jpeg_xl_images_in_pdfs/
https://info.aiim.org/aiim-blog/why-jpeg-xl-should-be-added-to-the-pdf-standard

JPEG-XL - Active Discussion

JPEG XL news and discussion on reddit
https://www.reddit.com/r/jpegxl/

Support JPEG XL - Page 13 - Mozilla Connect
https://connect.mozilla.org/t5/ideas/support-jpeg-xl/idi-p/18433/page/13

Request for re-opening the Request for position on JPEG XL · Issue #721 · mozilla/standards-positions · GitHub
https://github.com/mozilla/standards-positions/issues/721 Closed


JPEG XL (official community website)
https://jpegxl.info/


 

JPEG-XL - in Music

Give JXL a Chance
is a song that uses a popular melody to embrace the modern JPEG-XL image format, which is supported by a growing number of image viewing/editing applications - and maybe reach general browser support in 2024, we’ll see.