Chrome's CrUX adds experimental Core Web Vitals that count SPA soft navigations

For years, Core Web Vitals for a single-page app have grouped every click after the first one with the landing page, so a slow in-app view did not show up as its own number. Chrome is publishing experimental versions of all three Core Web Vitals in the Chrome User Experience Report that count soft navigations, the in-app URL and content changes an SPA makes without a full reload. The new fields are in BigQuery, the CrUX API and the History API from the October 2026 release, and CrUX Vis has a toggle to compare them to the stable versions.

The three new fields are experimental_largest_contentful_paint_with_softnavs and matching ones for INP and CLS. They measure the same things as the stable fields and add soft navigation events. The data comes from the Soft Navigations web platform API, on by default since Chrome 151 shipped on 28 July. Chrome treats a soft navigation as a user action that produces both a visible URL change and a visible paint.

Where the numbers move

Across all origins in CrUX, around 70 percent have little or no soft navigation traffic, which Google defines as fewer than 5 percent of page views being soft. Only about 7 to 11 percent of origins use soft navigations for more than half of their page views. Among the top 1,000 sites, that share rises to 35 percent on Android and 42 percent on desktop.

Google's post sorts origins by soft-navigation share and reports what happens on the right-hand side of that chart. For origins where more than 75 percent of page views are soft navigations, the share of Android sites passing the stable Largest Contentful Paint test is 26 percent; on the experimental metric that counts soft navigations, it is 87 percent. The release notes for the September dataset state that 55.9 percent of all origins passed Core Web Vitals when soft navigations were not counted, and 59.5 percent when they were.

Google writes that the gain is not because SPAs are faster than multi-page sites, but because follow-up clicks are faster on any site, so SPAs with many follow-up visits now compare against multi-page sites with many follow-up visits. Interaction to Next Paint is now measured per page view rather than taking the slowest interaction across a session, which roughly doubles Android pass rates for soft-navigation-heavy sites. SPA-heavy sites still trail multi-page sites on INP. Cumulative Layout Shift events are grouped by view rather than by session, which Google says brings SPA-heavy desktop sites level with multi-page sites, with Android still behind.

What stays the same for now

Stable Core Web Vitals scores are unchanged, and Search Console will keep using them until Chrome switches once the metrics graduate from experimental. The target for that is May 2027, subject to feedback. In the Web Vitals lifecycle, metrics move from experimental to pending for at least six months before becoming stable, and Google has not stated which of the two stages comes next for soft navigations. Experimental versions of First Contentful Paint and navigation types are expected in the November CrUX release.

A site that reloads every page on click will see no change. On an SPA, turning on the Include soft navigations toggle in CrUX Vis shows both versions of each metric side by side, which is where to look if performance work on in-app views has been invisible in the stable numbers so far. Google asks readers to expect month-to-month shifts while the measurement improves and to interpret the new numbers cautiously.

Source

• Experimental Core Web Vitals for Single-Page Applications in CrUX, web.dev
• Google Adds Experimental Soft Navigation Metrics To CrUX, Search Engine Journal