Skip to main content
Performance

Page Speed

Site Speed | Load Speed

Portrait of Lukas Horvath, co-founder of Roelu Studio
Lukas HorvathCo-founder

What is Page Speed?

Page speed is the umbrella term for how fast a web page loads and becomes interactive. It's measured across several metrics — Largest Contentful Paint, First Contentful Paint, Time to Interactive, and Total Blocking Time — rather than a single number. Page speed is a confirmed Google ranking factor for both search and Google Ads quality scores. Synonyms include site speed and load speed.

Why it matters

Page speed compounds. A 100ms improvement raises conversion rates roughly 1% in most published studies. On a Series B site with $5M in pipeline running through the homepage, that's not a rounding error. Slow sites also pay a paid-media tax: Google charges higher CPCs to advertisers with slow landing pages. The frustrating part is that page speed is mostly solved at this point. Modern stacks ship sub-second loads by default. If your site is slow, it's usually because someone glued together a builder and a dozen third-party scripts and called it a website. The fix is rarely incremental. It is architectural.

How it works

Page speed is measured two ways. Lab data is generated by simulated tests in tools like Lighthouse and WebPageTest, which give a consistent score for diagnosing issues. Field data — also called Real User Monitoring — is collected from actual visitors and reported in the Chrome User Experience Report and tools like Vercel Speed Insights and PostHog. The big speed wins come from a small set of moves: serve content from a CDN, optimise and lazy-load images, defer or remove third-party scripts, and ship server-rendered or static HTML rather than client-rendered JavaScript bundles. Stack matters more than tuning. A Next.js or Astro site on Vercel or Cloudflare starts fast and stays fast.

Related terms

  • Core Web Vitals

    Performance

    Google's three benchmark metrics that measure how fast a page loads, how quickly it responds to clicks, and how stable the layout feels as it renders — used in…

  • Largest Contentful Paint

    Performance

    The Core Web Vital that measures how long it takes for the biggest visible element on a page — usually the hero image or main headline — to finish loading in…

  • Image Optimization

    Performance

    Compressing, resizing, and serving images in modern formats so pages load faster without losing visible quality — usually the single biggest performance win…

  • Lazy Loading

    Performance

    A technique that delays loading images and other heavy assets until the visitor scrolls near them, making the rest of the page load faster and feel snappier.

  • Caching

    Performance

    Storing a copy of a page, image, or piece of data so it can be served instantly the next time it's requested — instead of regenerating it from scratch on every…

  • Content Delivery Network

    Performance

    A global network of servers that stores copies of your site close to visitors, so pages load fast in São Paulo, Sydney, and Stockholm without every request…

  • PageSpeed Insights

    Performance

    Google's free tool for measuring how fast a page loads on mobile and desktop, combining real-user field data with lab tests and offering specific, actionable…

  • Lighthouse Score

    Performance

    A 0–100 grade from Google's Lighthouse tool measuring a page's performance, accessibility, SEO, and best practices — used as a quick technical health check by…