Which apps support to open and convert JPEG XL (.jxl) pictures?

Question

JPEG XL (.jxl) is the next-generation, general-purpose image compression codec by the JPEG committee (more info you can find on jpegxl.info). Which apps/programs can open and convert it?

Answer 1

So far following apps support JPEG XL:

Viewers

• Geeqie – Recent commit adds JPEG XL support.

• gThumb (Linux image viewer) from version 3.11.3 onwards as Flatpak or with unofficial UbuntuHandbook PPA:

  sudo add-apt-repository ppa:ubuntuhandbook1/apps

• XnView MP – closed-source image viewer (but up to 0.99.1 JXL support limited to Windows)

• Gwenview (KDE Application)

• PhotoQt Image Viewer

• nomacs - Image Lounge

• qimgv - Image viewer. Fast, easy to use. Optional video support.

• digiKam - Advanced open-source digital photo management application, settings see here.

• PicView - Fast Picture Viewer

• Qt plug-in qt-jpegxl-image-plugin to allow Qt and KDE based applications to read/write JXL images.

Browsers

• Palemoon (from version 31.4.0 onwards)

Browsers with activation

• Firefox (see Tutorial), Chrome, Edge, Opera, Brave

Converters

• libjxl – JPEG XL Reference implementation
• MConverter – online media converter
• Squoosh – WebAssembly-based image converter
• jpegxl.io

Other:

• Thunderbird (Email client): To enable JPEG XL support: Tools -> Options -> Advanced -> General: Click on button Config Editor: Manually set image.jxl.enabled to true.
• Photostack - Open-source batch photo editor
• ExifTool – Official JPEG XL support added in version 12.25.
• darktable since version 4.2 - Open source photography workflow application and raw developer
• GIMP – With 2.10.32 the JPEG XL file format support was backported from the 2.99.8 development release, so far only with import ability (unofficial PPA for Ubuntu 21.10+, sudo apt install libjxl-gimp-plugin needed to get JPEG XL support).
  The libjxl repository includes a plugin for 2.10+.
  There is another plugin for development GIMP 2.99.
• ImageMagick – toolkit for raster graphics processing
• FFmpeg – multimedia framework, via libjxl
• Qt / KDE apps - via KImageFormats
• Squoosh App - Multiplatform desktop app to optimize, resize, compress and convert your images.

Answer 2

Here is a full list of all softwares and services that support JPEG XL, as of November 2021. This list (and the linked tutorials) are authored by me, as part of a project to create an ecosystem platform around the format:

Browsers:

1. Chrome (behind a flag, tutorial)
2. Firefox (behind a flag in the Nightly version, tutorial)
3. Edge (behind a flag, tutorial)
4. Opera (behind a flag, tutorial)

CDNs:

1. Only Cloudinary, on request

Toolkits, Libraries:

2. ExifTool (metadata)
3. Exiv2 (metadata)
4. KDE Frameworks
5. Library for PHP (decoding)

Converters

1. libvips (library)
2. jpegxl.io (support library & online conversion, client-side)
3. Squoosh (online conversion, client-side)
4. ImageMagick (toolset)
5. FileStar (conversion software)

Viewers:

1. Geeqie (*)
2. GwenView (*)
3. gThumb (*)
4. ImageGlass (*)
5. IrfanView
6. nomacs (*)
7. PhotoQt (*)
8. PhotoStack
9. PicView
10. XnView

** Should work with Ubuntu, either natively or with a third-party installer.

Edit: Added authorship notice!