Performance
Page Speed
Page speed is a colloquial term covering the time a page takes to become visually complete and interactive. It is measured by composite metrics like Core Web Vitals, Speed Index, and Time to Interactive.
In depth
There is no single 'page speed' number. Different metrics capture different aspects: TTFB (server speed), FCP (first paint), LCP (main content paint), TTI (time to interactive), TBT (total blocking time), and Speed Index (the average paint over time).
Google's PageSpeed Insights surfaces all of these and aggregates them into a 0-100 score using Lighthouse.
Why it matters
Page speed correlates directly with bounce rate, conversion rate, and SEO ranking. Amazon famously measured a 1% revenue drop for every 100 ms of additional load time. Optimising page speed is one of the highest-ROI engineering investments available.
Also known as
- Page load speed
- Site speed
How Lemwatch helps with page speed
Lemwatch monitors page speed continuously and alerts you the moment something changes.
Performance monitoring →Related terms
Lighthouse
Lighthouse is Google's open-source automated auditing tool for web pages. It produces a 0-100 score across per…
Core Web Vitals
Core Web Vitals are a set of three Google-defined metrics that measure real-user experience on a webpage: Larg…
TTFB
Time To First Byte (TTFB) measures how long after a request before the first byte of the response arrives. It …
LCP
Largest Contentful Paint (LCP) measures the time from navigation start until the largest visible element on th…
Real User Monitoring
Real User Monitoring (RUM) captures actual page load performance in real visitors' browsers — LCP, INP, CLS, T…
Browse the full Lemwatch monitoring glossary (47 terms).