JPEG XL 0.12.0 / JXL Winthumb 0.12.2

A folder of JPEG XL photos in File Explorer shows a grid of identical blank icons instead of pictures.

Windows has no built-in decoder for the format, so it cannot draw a preview and falls back to the generic file icon.

JXL WinThumb adds one.

What This Actually Does

Windows draws thumbnails and opens images through a system called the Windows Imaging Component, and every format it understands arrives as a small decoder plugged into it. There is no JPEG XL decoder in the box, which is the whole reason for the blank icons.

JXL WinThumb registers one. It is not an application and there is nothing to launch - after installing it, Windows has simply learned a new format.

Thumbnails appear in File Explorer, the preview pane works, and .jxl files open in Paint, in Microsoft Photos, and in any other program that reads images the standard Windows way.

Installing It

The installer here is built by xcodecpack.com. It detects whether your PC is 64-bit Intel or AMD, 64-bit ARM, or 32-bit, and registers the matching file.

It never restarts File Explorer. Earlier builds did, and on some Windows 10 PCs that left a black screen with no taskbar, so the installer now asks for a PC restart instead - and only when Explorer has already cached blank icons.

It checks the Visual C++ runtime before anything else and offers to download Microsoft's own package if it is missing or too old. It also adds a normal entry to Add or Remove Programs, plus two Start Menu shortcuts - Rebuild thumbnail cache and Repair JXL WinThumb.

Installing on several PCs? It runs silently with /S and returns exit code 3010 when a restart is still pending. Add /log=jxl.log to get a step-by-step log to attach to a support request.

Have iPhone photos as well? X Image Codecs installs JXL WinThumb and a HEIC codec together, with a checkbox for each.

If you would rather do it by hand, the one thing to get right is the filename. There are three, and the architecture is part of the name.

Open Command Prompt as administrator, change to the folder holding the file, and register it with regsvr32 jxl_winthumb_x86_64.dll, substituting your own filename. To remove it later, run the same command with /u after regsvr32.

The Other Files on the Download Page

The download page carries more than the installer, and only two of the files are JXL WinThumb. Pick by what you are trying to do.

When the Thumbnails Do Not Appear

This catches almost everyone who installs by hand, and it is not a failed installation.

Explorer caches the blank icons it drew before the decoder existed, and registering a codec does not clear that cache. It also loads decoders once when it starts, so a running Explorer will not notice a new one.

A restart deals with the second part. For the first, clear the cache in a way that leaves your desktop alone:

• Open Disk Cleanup from the Start menu and choose drive C:.
• Tick Thumbnails - you can untick everything else - and click OK.
• Restart the PC. Explorer builds fresh thumbnails as you browse.

Used the installer? Start > X Codec Pack > JXL WinThumb > Rebuild thumbnail cache does the same job and offers the restart. If icons are still blank after that, the file is genuinely not registered, so run Repair JXL WinThumb from the same folder.

Where This Build Stands

Worth being straight about, because it affects whether you should use this or the Microsoft extension.

The current release is version 0.2.12, from 31 August 2025, and nothing has shipped since. The decoder inside it is a separate open-source project called jxl-oxide, at version 0.12.4 - which is where the "0.12.4" you see quoted around the web comes from, including in older versions of this page.

That decoder has moved on. jxl-oxide 0.12.6, released in May 2026, fixed three reported flaws in its image-parsing code, one of which affects 32-bit builds specifically. JXL WinThumb has not been rebuilt against it.

In practice these are the kind of faults that make a decoder crash or misbehave on a deliberately malformed file rather than known break-ins, and none has a published exploit. But this is a decoder Explorer runs by itself the moment you open a folder, so it is worth knowing.

Who Should Look Elsewhere

Three tells, each checkable before you download anything.

• Your winver says 26100 or higher. Press Windows and R, type winver, and read the build number - if it is 26100 or above you are on 24H2 and should take the maintained Microsoft extension instead.
• You only want to look at the files, not fix Explorer. A viewer that reads JPEG XL on its own needs nothing installed system-wide - IrfanView with its plugins, XnView, JPEGView or PicView all open them directly.
• You need to edit them, not view them. This is a decoder and nothing more - GIMP reads and writes JPEG XL itself and does not care whether Windows understands the format.

The How to View JPEG XL Files on Windows guide walks through every route including the ones above, and the Image Viewers section lists the rest.

What It Will Not Do

It decodes pixels, and that is the whole job. EXIF and IPTC information written by Lightroom, Photoshop or your camera does not show up in the Explorer details pane, and sorting a folder by date taken will not work on .jxl files.

That is not a bug in this codec. Windows reads metadata through a different component called a property handler, and nobody has written one for JPEG XL, so there is nothing on Windows that surfaces those fields today.

The data is still in your files and readable. ExifTool shows and edits every tag JPEG XL can carry.

Converting and Sharing JPEG XL

Viewing is one problem and sending is another, because most websites, chat apps and email clients still reject .jxl uploads.

For one file, convert JXL to JPG in the browser with nothing to install.

For a whole folder, XL Converter handles JPEG XL, AVIF, WebP and HEIF with multithreaded batches, and Converseen covers a wider spread of formats if your library is mixed.

JPEG XL is worth the trouble. It stores the same picture at roughly half the size of a JPEG, keeps a genuine lossless mode, and handles HDR and transparency - which is why Apple adopted it for iPhone camera capture, covered in the iPhone 16 JPEG XL guide.

If JPEG XL is not the only format giving you blank icons, four more decoders close the rest of the gaps:

• WIC for HEIC for iPhone photos, with no Microsoft Store extensions.
• WebP Codec for the format most of the web now serves.
• libavif for AVIF, common in Android screenshots and newer sites.
• Raw Image Extension for Canon, Nikon, Sony and Fujifilm camera files.

Quick questions

More decoders, converters and image tools sit in the Graphics section.

Download JXL WinThumb 0.2.12 and see how it handles your files, or tell us how you got on if you have used it before.