In October 2026, JPEG XL got in a single week what it had been waiting years for: on 6 October Chrome 155 enabled it by default, and on 13 October Firefox 158 followed. Nine days after the Chrome release, John Mueller of Google reminded everyone that Google Images and Discover previews do not support the format. If you are planning to switch your images to .jxl because browsers can finally read them, this is exactly the moment when it is easy to hurt your own SEO. Below I go through what Mueller actually wrote, what the documentation says, where browsers stand after the October releases, and how I would roll the format out myself.

What John Mueller wrote

On 15 October 2026 Mueller posted on Bluesky that if you want your images to show up in Google Images and as previews in Discover, JPEG XL “is currently not supported”, and linked to the documentation. Barry Schwartz covered it on 23 October in Search Engine Roundtable, and from there it spread through the industry.

The Google Search Central documentation leaves no room for interpretation. Search supports images referenced in the src attribute of img in BMP, GIF, JPEG, PNG, WebP, SVG and AVIF, and the file extension should match the file type. JPEG XL is not on that list, and Mueller did not announce that it would be.

The statement itself adds nothing new, because the list of formats has looked like this for a long time. What is new is the context: for the first time the format works by default in the major browsers, so someone is about to deploy it in production and only then run into that list.

What changed in browsers in October 2026

As recently as this spring, the JPEG XL decoder in Chrome sat behind a flag, and in Firefox it was available only in Nightly builds. Many guides online, including ones written in 2026, still describe that state. October changed it:

BrowserJPEG XL supportSince
Chrome 155 and Chromium-based browsers (e.g. Brave 1.97)decoding enabled by default, jxl-rs decoder written in Rust6 October 2026
Firefox 158enabled by default13 October 2026
Safarisupported since Safari 17; according to the Core Web Vitals site partial, without animation and progressive decoding2023

In its post on the Chrome for Developers blog, Google says JPEG XL compresses 30-50% better than JPEG, supports lossless compression and HDR, and allows existing JPEG files to be transcoded losslessly. The second half of that post is the more interesting one. Google recommends trying both AVIF and JPEG XL, and expects the new format to be most useful for photography, high-fidelity and lossless compression, and wherever progressive decoding matters. Google therefore treats JPEG XL as an extra option to compare, not as a successor to AVIF. The whole post covers decoding only.

The road to this point was long. In 2022 Google removed experimental support from Chrome, explaining that the ecosystem showed too little interest and that the format did not bring enough benefit over existing ones to enable it by default. In January 2026, as The Register reported, the jxl-rs decoder landed in the Chromium codebase, a Rust implementation in place of the reference libjxl in C++. For Mozilla that was the condition: back in 2024 the Firefox team said it would consider JPEG XL once a Rust decoder existed, because of safety concerns about roughly 100,000 lines of multithreaded C++ code in libjxl. The same decoder therefore unlocked both browsers.

The browser and the search engine are two different things

These are the two levels that are easiest to confuse. The browser decides whether a visitor sees the image on your page. Google’s indexing systems decide whether that image makes it into Google Images, result thumbnails and Discover previews. After October, the first condition is met for JPEG XL in all three major engines, the second still is not.

There is also a third level that is easy to forget in a discussion about Google: social networks and messaging apps that fetch the Open Graph image. In my experience they expect JPEG or PNG and have never heard of JPEG XL. That is my practical assessment, not a statement from any of those companies, but at deployment time it matters just as much as Google’s list.

How this affects image SEO

In audits I see sites losing image visibility mainly through the quality of the implementation: missing alt text, images injected by script after the page loads, thumbnails without a page where the image sits in a meaningful context. The format is rarely the culprit, because almost everyone uses JPEG, PNG or WebP. With JPEG XL it would become the culprit immediately.

What you risk by switching the format

If an article’s main image or a product photo is available only as .jxl, Google gives no guarantee that it will use it. In practice that means no or limited presence in Google Images and a weaker card in Discover, where a large image goes a long way towards deciding click-through. On top of that comes the Open Graph problem described above.

A separate trap waits for anyone using a CDN with automatic format negotiation based on the Accept header. Such a server decides on its own what to send to each client, and there is no telling how it will behave towards Google’s crawler once image/jxl joins the list of formats. Before you enable JPEG XL in that setup, check in your logs what Googlebot-Image actually receives.

The safe pattern: a picture element with a fallback

If you want to test JPEG XL right now, use the picture element. The browser picks the first source it supports, and the img with a format from Google’s list is always the final fallback:

<picture>
  <source srcset="photo.jxl" type="image/jxl">
  <source srcset="photo.avif" type="image/avif">
  <source srcset="photo.webp" type="image/webp">
  <img src="photo.jpg" alt="Image description" width="1200" height="800">
</picture>

The src attribute of img should point to a format from Google’s list. The documentation talks specifically about images in the src of img, so that is where the file meant for the index has to be. I do not take this as confirmation that Google will simply skip a source with JPEG XL, and Google’s own post about Chrome 155 contains no guidance on picture or fallbacks. It is, however, the safest arrangement I know.

What will improve results instead

If the goal is faster loading rather than the format itself, you already have supported options at hand. AVIF and WebP usually deliver large savings over JPEG, and both are on Google’s list. The impact on LCP and on Core Web Vitals in general depends far more on correct dimensions, the loading priority of the main image and the absence of lazy loading on the LCP element than on a change of format. I cover how images work in visual search in more depth in my article on optimising content for visual search.

What remains unknown

On 23 October 2026 Glenn Gabe noticed indexed .jxl files in Google Images, and a filetype query returns them alongside other formats. An interesting observation, but it does not contradict Mueller, because presence in the index does not mean official support, stable behaviour or presence in Discover. Nor is it known whether this is a side effect, a test or a handful of isolated cases.

There is also no information on whether or when Google will add JPEG XL to the documentation. Since the same company ships the decoder in Chrome and praises the format on its own blog, my guess is that it is a matter of time, but that is only my assumption. Planning a rollout on that basis would be gambling with someone else’s money.

Summary

After October 2026, JPEG XL finally has the browsers on its side, but for image visibility in Google it is still not safe. The documentation lists BMP, GIF, JPEG, PNG, WebP, SVG and AVIF, and Mueller confirmed that this is the current state. If you experiment with .jxl, do it inside a picture element, keep a format from Google’s list in the src of img, and with a format-negotiating CDN check what the crawler receives. After deployment, watch the Search Console performance report filtered by the “Image” search type, because that is where you will see fastest whether something broke.

Frequently Asked Questions

Does Google Images support JPEG XL?

No. Google documentation lists BMP, GIF, JPEG, PNG, WebP, SVG and AVIF, and John Mueller confirmed on 15 October 2026 that JPEG XL is currently not supported.

Will JPEG XL images appear in Google Discover?

Mueller pointed out that JPEG XL is not supported for Discover previews either. If Discover matters to you, keep the main image in JPEG, PNG, WebP or AVIF.

Which browsers support JPEG XL?

Chrome from version 155 (6 October 2026) and Firefox from version 158 (13 October 2026) decode JPEG XL by default. Safari has supported the format since version 17, according to the Core Web Vitals site without animation and progressive decoding.

Is it worth switching to JPEG XL for faster page loading?

For now it is safer to choose AVIF or WebP, which Google supports in Search. Google itself advises comparing AVIF and JPEG XL on your own images. Test JPEG XL with a fallback in the picture element and a supported format in img.

If .jxl files show up in Google Images, does that mean the format works?

No. Glenn Gabe spotted indexed .jxl files, but the official documentation does not list them. Presence in the index is no guarantee of support.

Sources

  1. Search Engine Roundtable: JPEG XL Image Format Not Supported By Google Images & Google Discover https://www.seroundtable.com/google-jpeg-xl-42352.html
  2. Google Search Central: Image SEO Best Practices: Use supported image formats https://developers.google.com/search/docs/appearance/google-images#supported-image-formats
  3. Bluesky: John Mueller on the lack of JPEG-XL support (15 Oct 2026) https://bsky.app/profile/johnmu.com/post/3mxw5yrrd322v
  4. Chrome for Developers: Shipping JPEG XL in Chrome https://developer.chrome.com/blog/jpeg-xl-in-chrome
  5. Firefox: Firefox 158.0 Release Notes https://www.firefox.com/en-US/firefox/158.0/releasenotes/
  6. JPEG XL: Software Support https://jpegxl.info/resources/software-support.html
  7. The Register: Google rekindles relationship with jilted JPEG XL image format https://www.theregister.com/2026/01/14/google_rekindles_relationship_with_jilted/
  8. Core Web Vitals: JPEG XL and Core Web Vitals: what you need to know now that Chrome ships it https://www.corewebvitals.io/pagespeed/jpeg-xl-core-web-vitals-support