FAQs

JPEG XL is a next-generation image compression format designed to provide efficient compression with significant improvements over traditional JPEGs, WebP, HEIC and AVIF images in both quality and file size. It is optimized for images delivered at web quality through lossless levels. The codec was designed to allow its users to balance three primary criteria:

• high fidelity to the source image
• encoding and decoding speed
• compression ratio (typically 20:1 to 50:1)

JPEG XL combines several modern compression techniques to reduce file sizes while preserving visual quality. Unlike traditional JPEG, it uses a perceptual encoding model that prioritizes the details people actually see, allowing it to remove less noticeable information more efficiently. It also supports both lossy and mathematically lossless compression, progressive decoding, efficient handling of HDR and wide-gamut images, and reversible transcoding of existing JPEG files. Together, these technologies enable JPEG XL to deliver higher image quality at smaller file sizes than older image formats.

• Smaller file sizes: This translates to faster loading times for web pages and reduced storage requirements – often up to 65% smaller.
• Improved image quality: JPEG XL offers better image fidelity than all current compression algorithms.
• Support for forward-looking features:
  • lossless compression
  • visually lossless compression
  • transparency
  • animation, layers & thumbnails
  • web-friendly progressive encoding and decoding
  • improved color accuracy and color gamut support through HDR (high dynamic range) and high bit depth support

JPEG XL makes a great replacement for JPEG, as it includes several features that ease the transition from the legacy JPEG format. Most critically, it supports lossless JPEG transcoding, converting any ‘classic’ JPEG into JPEG XL with bit-for-bit quality while saving an average 20% in file size. If needed, these files can be restored to the exact original JPEG, ensuring backward compatibility with existing JPEG-based applications

It will take time for JPEG XL to be fully adopted. Because it offers significant advantages to all competing formats, it will likely become the new standard for image compression.

Yes, JPEG XL is free to use and fully open sourced. The reference encoder can be found here.

JPEG XL is not optimized for very low-quality compression levels. At such file sizes, video codecs like AVIF tend to produce better results due to their specialized algorithms for low-bitrate compression.

This site – jpegxl.info – is a community website dedicated to providing information, tools, and resources about JPEG XL. It offers current information about the format, its benefits, and how to use it. Feel free to add to it!

Smaller file sizes lead to reduced bandwidth usage and energy consumption during storage and transmission.

JPEG XL is the official name.

Use JPEG XL, not JPEG-XL or JPEGXL. JXL is a common abbreviation and the file extension (.jxl).

JPEG XL is well-suited for applications where both image quality and file size are critical, including websites, photography, and graphic design. It enjoys wide support within the Apple ecosystem, Adobe’s photography tools, and various image libraries. For a comprehensive list of supported platforms, refer to this Github page.

While JPEG XL offers numerous benefits, there are some limitations to consider. The most significant limitation is that browser support for JPEG XL is still evolving, meaning not all browsers can display JPEG XL images natively. Additionally, some existing image editing software might not yet offer native support for JPEG XL, requiring updates or plugins to handle the format. Therefore, users may need to rely on compatible software and browsers to fully utilize JPEG XL’s capabilities.

Support for JPEG XL in web browsers is still evolving. Most modern browsers offer support, but it’s not yet universally adopted. It’s fully supported in Safari, Thorium, Basilisk, Pale Moon, and Waterfox, and behind a flag in Chrome, Firefox and Opera. You can check https://caniuse.com/jpegxl for the latest browser compatibility information.

Leverage the <picture> element to deliver JXL images to browsers that support them, while ensuring fallback for other browsers:

<picture>
   <source srcset="photo.jxl" type="image/jxl">
   <source srcset="photo.webp" type="image/webp">
   <img src="photo.jpg" />
</picture>

jpegxl.info offers documentation, tutorials, resources to help you learn more about using JPEG XL format. You can also find many links to relevant articles and tools on the site.

The official JPEG committee JPEG XL site can be found here: https://jpeg.org/jpegxl/

There is a subreddit about JPEG XL, and informal chatting with developers and early adopters of libjxl can be done on the JPEG XL Discord server.

You can report issues or bugs with JPEG XL to the JPEG XL community of developers through its Github page.

There are various tools and online converters available that can convert images to JPEG XL format. Some image editing software may also offer JPEG XL export options. Many open-source software packages such as Gimp, Krita, and darktable, as well as proprietary software such as Adobe Camera Raw and Affinity Photo have all added support for JPEG XL. The reference software libjxl comes with command-line tools (cjxl and djxl) to convert images from other formats to JPEG XL and back. Various other popular command line tools such as ImageMagick’s convert and FFmpeg also have JPEG XL support.

Not at all! JPEG XL is designed for computationally efficient encoding and decoding using software implementations – on today’s hardware – without the need for additional hardware acceleration, even on mobile devices.

Both JPEG XL and WebP offer significant improvements over JPEG. However, they have some key differences:

• Inherent Limitations: WebP’s maximum of 8 bits-per-channel and its mandatory use of 4:2:0 chroma subsampling in lossy images restrict its suitability for high-quality image applications. In practice, lossy WebP operates at 6.5 bits per pixel rather than 8 bits. While the green channel retains approximately 7 bits of precision, the red and blue channels lose more than one bit of accuracy due to their conversion into a limited-range YUV format. WebP also limits image width and height to 16,383 pixels. While this may suffice for most web use cases, it is not practical for authoring workflows and other applications where larger image dimensions are required.
• Compression algorithms: JPEG XL employs a more complex compression pipeline compared to WebP, leading to better compression ratios versus compression speed at all levels. [link]
• Feature support: JPEG XL offers a wider range of critical modern features like HDR & wide gamut support, 32 bits per channel, progressive decoding, extra channels, and CMYK support, making it more versatile for various applications.
• Browser adoption: WebP currently has wider browser support compared to JPEG XL.

JPEG XL itself doesn’t have a pre-defined maximum file size. There are theoretical limits based on the way the format works, but in practical terms, the maximum size is more likely to be restricted by other factors like software and storage limitations.

JPEG XL supports images up to 1,073,741,823 × 1,073,741,823 in resolution, making it suitable for high-resolution images and the most demanding applications.

JPEG XL achieves an average compression efficiency of 1.3× to 2× better than JPEG for equivalent quality images. This varies depending on the type of image.

Yes, JPEG XL absolutely supports various color gamuts! This is one of its key advantages over traditional JPEGs (and WebP).

Here’s a breakdown of its capabilities:

• Wide Color Gamut Support: JPEG XL is designed to handle images with a wider color range than the standard sRGB color space. This allows for more accurate representation of colors, especially those seen in high-quality photographs or graphics.
• ICC Profiles: It supports embedding ICC profiles within the image file. These profiles define the specific color space used, ensuring consistent color interpretation across different devices. This is crucial for professional applications where accurate color reproduction is essential.
• Flexibility: JPEG XL is flexible in handling various color depths with support for bit depths up to 32 bits per channel.

JPEG XL supports everything from standard 8-bit images through 10-bit, 12-bit, 16-bit, and even 32-bit floating-point content. Unlike most image formats, however, JPEG XL’s lossy encoder doesn’t depend on fixed bit-depth modes. It works in an internal floating-point color representation and optimizes for what people actually see, not simply how many bits were used to store the original pixels. This makes JPEG XL particularly well suited to HDR, wide-gamut imaging, professional editing workflows, and future display technologies.

While JPEG encoding is generally faster on the surface, the truth is more nuanced.

• Configurable Compression: Just like JPEG has different encoders with varying speed and quality options (like the slower but higher-quality MozJPEG compared to libjpeg-turbo), JPEG XL’s libjxl lets you fine-tune the balance between speed and compression. It offers settings to prioritize getting the job done quickly, even if it means sacrificing some compression. This can be helpful when you need to encode images quickly, like for real-time applications.
• Modern Hardware : Both JPEG and JPEG XL encoding are very fast on modern hardware, making the speed difference often insignificant.
• Multi-Core Support: Unlike JPEG, JPEG XL excels at utilizing multiple cores, making it potentially faster for encoding and decoding on multi-core CPUs. This means with enough cores, JPEG XL can compress faster than jpeg.

JPEG decoding is faster than JPEG XL decoding, but JPEG XL is designed to be highly parallelizable. Both decode in the blink of an eye. JPEG XL decoding is still under development and is expected to see further optimizations in the future, potentially narrowing any gap.

Yes. JPEG XL can detect corruption caused by transmission or storage errors, helping prevent damaged files from being decoded incorrectly. It does not include built-in error correction, however, because correcting errors requires storing extra redundant data that reduces compression efficiency. As with most image formats, error correction is expected to be handled by the underlying storage system or network protocol rather than the image codec itself.

Yes. JPEG XL fully supports modern metadata standards, including EXIF, XMP, JUMBF, and Coalition for Content Provenance and Authenticity (via JPEG Trust). This allows images to retain everything from camera settings and editing information to copyright, AI provenance, and content authenticity credentials. JPEG XL can also optionally compress metadata using Brotli⁠ compression, making metadata more space-efficient than traditional JPEG while remaining fully lossless.

JPEG XL supports animation, image sequences, photo bursts, and multi-pages.

JPEG XL supports not just alpha channels (it’s even possible to add alpha to existing JPEGs!), but depth maps, thermal channels, spot colors and selection masks. The extra channels can optionally be subsampled. JPEG XL also allows creating layered images, where the layers are blended according to the alpha channel.

Yes. JPEG XL can losslessly transcode an existing JPEG so that no image data is lost. When transcoded with cjxl and later converted back to JPEG with djxl, the original JPEG bitstream is reconstructed bit-for-bit, producing an identical JPEG file. In other words: JPEG XL isn’t re-encoding the JPEG image. It’s preserving the original JPEG codestream inside the JPEG XL file so it can be restored exactly later.

The only caveat is that two different JPEG decoders may still render the image with extremely small visual differences. That’s not caused by JPEG XL. It stems from the JPEG standard itself, which allows some implementation-specific variation in how images are decoded. The original JPEG data, however, is preserved exactly.

Other encoders may or may not support lossless transcoding, so it’s best to check any support documention to verify. Note that lossless encoding of a JPEG file to JPEG XL is not the same as lossless transcoding. Transcoding uses a specific mode to achieve its 20% size saving while maintaining pixel-level accuracy.

The JPEG XL format is under continuous development, with efforts towards:

• Improving encoding/decoding speed: Although already leading against all other compression formats in compression size vs compression speed, the team aims to further optimize the algorithms to achieve faster processing times for both encoding and decoding.
• Improving compression density: JPEG XL boasts a highly flexible bitstream, opening doors for exciting encoder advancements. This flexibility allows researchers to explore new techniques for optimizing trade-offs between image quality and file size. For lossless compression, it paves the way for further improvements in both file size and compression speed.
• Expanding browser support: Collaborating with browser vendors to ensure broader browser compatibility for JPEG XL images.
• Enabling broad software support: We’re actively working with software vendors to integrate JPEG XL encoding and decoding capabilities into their applications, facilitating wider adoption across various workflows.