The Web Vitals extension is a Chrome-based measurement tool built by the Google Chrome team to surface Core Web Vitals metrics — LCP, INP and CLS — as you browse. A toolbar badge flips between green, amber and red to reflect the current page's scores using the same methodology Chrome uses when reporting to PageSpeed Insights, Search Console and the Chrome UX Report. Clicking the icon opens a detailed panel with per-metric breakdowns, contributing elements and debugging information.
A distinguishing feature is its integration with the Chrome UX Report (CrUX) API: the popup overlays your local experience against aggregated real-user data for the same origin, giving immediate context on whether a problem is specific to your machine or systemic across users. The extension also offers an overlay HUD showing metrics live while you interact with the page — invaluable when diagnosing layout shifts, slow paints or laggy input handling without opening DevTools.
Google announced end of life for the standalone extension on January 7, 2025, after the same capabilities (and additional real-time metrics) landed natively in the Chrome DevTools Performance panel in Chrome 129+. The source code remains on GitHub at GoogleChrome/web-vitals-extension for teams that still rely on it, and the underlying web-vitals JavaScript library continues as the canonical way to measure Core Web Vitals programmatically in production.
