Home / PageSpeed Metrics PageSpeed Metrics Metrics to help understand page speed and user experience. Collection 689 stars GitHub Contents Concepts Field Data (Real User Monitoring - RUM) User-centric metrics Rendering metrics (Hero) Element Timing Interactivity metrics First Input Delay (FID) Time to Interactive (TTI) Network metrics Concepts Field Data (Real User Monitoring - RUM) Web Vitals 8.5k updated 9d ago Open Source Library to collect Field Data. Perfume.js Open Source Library to collect Field Data. User-centric metrics Total Blocking Time (TBT) 688 updated 2y ago Is it usable - Can users interact with the page, or is it still busy loading? (e.g TBT) Rendering metrics Spec - LCP - W3C 99 updated 1mo ago https://github.com/WICG/largest-contentful-paint#readme Spec - Layout Instability API - W3C 165 updated 4mo ago https://github.com/WICG/layout-instability Spec - Element Timing API 60 updated 1mo ago (Hero) Element Timing Docs - Last Painted Hero - WPT 3.2k updated 7mo ago https://github.com/WPO-Foundation/webpagetest/blob/master/docs/Metrics/HeroElements.md Interactivity metrics First Input Delay (FID) Polyfill - FID 347 (archived) https://github.com/GoogleChromeLabs/first-input-delay Time to Interactive (TTI) Spec - TTI - Lighthouse https://docs.google.com/document/d/1GGiI9-7KeY3TPqS3YT271upUVimo-XiL5mwWorDUD4c/edit Network metrics Which third party scripts are most excessive 1.1k updated 13d ago Measuring own (and third-party) JavaScript bytes is crucial as JavaScript is the main cause of high TTI or FID values.
