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CWV Live

Your tab's real Core Web Vitals, live

chromeedgebraveoperafirefox🔒 Zero telemetryVersion 1.0.0
Download the extension for ChromeDownload the extension for Firefox

Description

Measures the real Core Web Vitals (LCP, CLS and an INP estimate) of the active tab's actual navigation, straight from the page via PerformanceObserver — SPAs included. Every metric is rated against Google's official thresholds and colored green/yellow/red. 100% offline, zero telemetry, no data ever leaves the browser.

Features

  • LCP (Largest Contentful Paint) from real navigation, with a buffered observer to capture the already-finalized value
  • CLS (Cumulative Layout Shift) summing only shifts without recent user input
  • INP/interactivity estimate based on the maximum observed interaction duration (event/first-input)
  • Color-coded good/needs-improvement/poor verdict per Google's official thresholds (web.dev/vitals)
  • Re-measure button for a fresh sample after interacting with the page
  • Works on SPAs and client-side rendered content, with no persistent host permissions
  • 100% offline and privacy-first: no network requests, no telemetry

Privacy

100% local processing in your browser. Zero telemetry: no data is sent to external servers.

Required permissions

  • activeTab
  • scripting

Screenshots

CWV Live

Supported browsers

chromeedgebraveoperafirefox