Convert JPG to JPEG XL

What JPEG XL is

JPEG XL (.jxl extension) is an image format standardized in 2021 by the same committee that created the original JPEG. Unlike WebP and AVIF, which come from video codecs, JPEG XL was designed from scratch for still images, and it shows in its features:

• Better compression than JPEG: at equal perceived quality, it typically takes 30% to 45% less space.
• Excellent at high qualities. Where AVIF tends to smooth fine textures (skin, grass, fabric), JPEG XL keeps the grain. It's the preferred format for quality photography and archiving.
• True progressive decoding: the image first appears at low resolution and refines as it downloads.
• A lossless mode that beats PNG, plus support for high dynamic range (HDR), alpha channels and bit depths up to 32.
• Fast encoding and decoding, much faster than AVIF.

How to convert JPG to JPEG XL

1. Drag your .jpg files onto the drop zone, or select a folder.
2. JPEG XL is already selected. A quality of 80 roughly matches a quality-90 JPG; for archiving you can go up to 90 or turn on Lossless.
3. Click Convert. Compare visually with the original using the before/after viewer and download the .jxl files.

ImageZap uses libjxl, the reference implementation, compiled to WebAssembly and running in your browser.

Compatibility: where a JXL can be viewed

This is JPEG XL's weak spot today, and it's worth being clear about before converting:

So for a website, JPEG XL should always be served with a fallback format using <picture>, so each browser picks the best one it understands:

<picture>
  <source srcset="photo.jxl" type="image/jxl">
  <source srcset="photo.avif" type="image/avif">
  <img src="photo.jpg" alt="Description" width="1600" height="1067">
</picture>

You can generate all three formats at once by selecting JPEG XL, AVIF and JPEG in the settings; ImageZap also gives you the <picture> code ready to copy. We explain it in detail in the guide WebP vs AVIF vs JPEG XL.

A note on "lossless recompression"

One of JPEG XL's best-known features is that it can losslessly recompress an existing JPG, saving around 20% and allowing the original JPG to be restored bit for bit. That feature requires working with the JPEG's internal data (its DCT coefficients) and is available in the cjxl command-line tool.

ImageZap, instead, decodes the image to pixels and re-encodes it. That lets you resize, change the quality or combine it with other formats, but the result can't be turned back into the original JPG. If you need strictly reversible photo archiving, use cjxl photo.jpg photo.jxl.

When it's worth it

• Photo archives and portfolios where quality at large sizes matters.
• Sites with a lot of Safari traffic (especially mobile iOS), serving it inside <picture>.
• Editing workflows: JPEG XL supports 16-bit and HDR, and professional editors already open it.

If you just want to cut weight on the web with maximum compatibility, AVIF or WebP are more practical today.

Frequently asked questions

Is JPEG XL better than AVIF?

It depends. At aggressive compression, AVIF usually wins on size. At high qualities, JPEG XL preserves detail better and is faster. On the web the ideal is to offer both with <picture>.

Why can't I open the .jxl in my browser?

Because Chrome, Edge and Firefox don't display it by default yet. Open it in Safari or a compatible editor.

Is EXIF metadata kept?

No. Re-encoding removes metadata, including GPS location. More in the guide on EXIF metadata.

Are my photos uploaded to a server?

No. The conversion happens entirely in your browser.