PageSpeed Insights scores may change after Lighthouse 13.6 update

PageSpeed Insights is now using Lighthouse 13.6.0, and that can change performance scores even when a page itself has not changed. According to Search Engine Journal, the updated Lighthouse version changes how PageSpeed Insights simulates load time and may produce higher lab scores, especially on JavaScript-heavy sites.

The update also changes how Lighthouse checks for Agentic Resource Discovery, or ARD, files. That means some technical checks in Lighthouse reports may look different after the switch.

What changed

Lighthouse 13.6.0 was released on October 27, 2026, and PageSpeed Insights is now using it. Barry Pollard said the update improves the simulated First Contentful Paint and Largest Contentful Paint and should make those measurements more accurate. He also noted that sites that rely heavily on JavaScript are more likely to be affected.

The underlying simulation, called Lantern, now uses Chrome’s own render-blocking label for requests when available. It also changes how simulated LCP is estimated when the main content is text that appears in the same frame as the page’s first content. Separately, the ARD audit now checks for an Agentmap line, a rel=”ard” link tag or Link header, and /.well-known/ard.json before checking older ai-catalog locations.

What it means for your website

If your PageSpeed Insights score went up recently, that does not automatically mean your website got faster. Part of the improvement may come from the new Lighthouse version rather than from changes on the page. This matters if you track lab scores over time or report performance gains internally.

It is also a reminder that the score shown in PageSpeed Insights is lab data from a simulated test. The same report also includes field data from real Chrome users over the last 28 days through CrUX. Search Engine Journal noted that before comparing results, it is worth checking whether both reports used the same Lighthouse version and then reviewing the field data as well.

What to do now

• Check the Lighthouse version shown in PageSpeed Insights before comparing a new report to an older one.
• If a score changed, review the field data in the same report to see whether real user experience changed too.
• Be careful about claiming a speed improvement unless the reports were generated with the same Lighthouse version.
• If your site uses a lot of JavaScript, expect a higher chance of seeing score changes from this update alone.
• If you use ARD, confirm that Lighthouse can find it through an Agentmap line, a rel=”ard” link tag or Link header, or /.well-known/ard.json.