Lighthouse 13.6.0 was on PageSpeed Insights by November 2, 2026, when Chrome web performance advocate Barry Pollard said the update was live there. It changes the model behind Lighthouse’s simulated lab results, so a score can shift even if the page itself has not changed. The project published version 13.6.0 on October 27, 2026.
Pollard expects the revised simulated First Contentful Paint (FCP) and Largest Contentful Paint (LCP) results to be more accurate and usually produce better scores. He said JavaScript-heavy sites are more likely to be affected, and that the changes are not specific to single-page applications (SPAs). Pollard’s announcement
What Lighthouse 13.6.0 changes
Lighthouse uses Lantern to simulate how a page loads. Version 13.6.0 updates that simulation’s network and dependency modeling, as well as the Agentic Resource Discovery (ARD) audit. The official release notes list these changes:
| Area | Lighthouse 13.6.0 behavior |
| Render-blocking requests | Uses Chrome’s protocol renderBlocking status to set render-blocking priority. |
| Text LCP and FCP | Uses FCP graphs when text LCP occurs in the same frame as FCP. |
| Network simulation | Treats HTTP/3 connections as multiplexed; credits consumed HTTP/2 overflow bytes across simulation steps; excludes connectionless requests from active connection counts; and improves origin round-trip time (RTT), throughput and redirect handling. |
| ARD audit | Updates to ARD v0.91 and discovers manifests through HTTP Link headers, <link rel="ard"> and /.well-known/ard.json. It also warns about legacy ai-catalog locations. |
The changes affect how Lantern models request priority, page dependencies and network behavior when estimating loading metrics. Pollard’s expectation of generally better simulated scores is not a prediction of a particular result for every site.
The ARD audit also moves on from the older discovery names associated with Lighthouse 13.5. Our earlier coverage of Lighthouse 13.5 explains that version’s mismatch with current ARD discovery conventions; 13.6.0 recognizes the newer manifest paths and relations.
How to read PSI lab scores alongside CrUX
PageSpeed Insights lab results come from Lighthouse’s simulation. Its field data comes from the Chrome User Experience Report (CrUX), which reflects real visits. Google’s PageSpeed Insights documentation describes these as different kinds of measurement; PSI’s field-data window covers the previous 28 days.
For a before-and-after comparison, check which Lighthouse version produced each lab result and consider CrUX field data separately. A lab-score change across the move to 13.6.0 can reflect the revised simulation, not a change to the site.
