What is Page speed?

Page speed is how quickly a page loads and becomes usable. It isn’t one number. A page can start drawing quickly and still feel slow if it freezes on the first tap, so speed is measured with several metrics, each capturing a different moment:

• Server response — TTFB
• Visible loading — First Contentful Paint and Largest Contentful Paint
• Responsiveness — Interaction to Next Paint
• Stability — Cumulative Layout Shift

LCP, INP and CLS together form Google’s Core Web Vitals.

Why it matters for SEO

Speed influences search in three ways. Core Web Vitals are part of Google’s page experience signals, although relevance comes first. Fast, reliable server responses let Googlebot crawl more pages in the same time. And the biggest effect is indirect: slow pages lose visitors before they read, buy or link.

Lab data versus field data

PageSpeed Insights shows both. When they disagree, field data is the truth for your users and for Google.

Where the time usually goes

1. Images — oversized JPEGs and PNGs instead of WebP or AVIF at the size they are displayed.
2. JavaScript — frameworks, sliders, chat widgets and tag managers, each adding download and main-thread work.
3. Render-blocking CSS and scripts in the head.
4. No caching or compression, so every visit re-downloads static files at full size.
5. Slow hosting and uncached, database-heavy pages.

Quick check: are the basics in place?

$ curl -sI -H "Accept-Encoding: br, gzip" https://example.com/app.css
HTTP/2 200
content-encoding: br
cache-control: public, max-age=31536000, immutable

Static files should come back compressed (Brotli or gzip) with a long cache lifetime and a versioned file name, so a new release gets a new URL. HTML should be compressed too, with a much shorter cache.

Common mistakes

• Chasing a perfect Lighthouse score instead of passing Core Web Vitals in field data.
• Installing a speed plugin on top of a heavy page builder, then a second plugin to fix the first.
• Testing only the homepage on office Wi-Fi.
• Treating speed as a one-off project. Every new tag, font and widget adds weight; agree on a budget and check it before each release.

Test your page

The page speed test measures server response time, download time, HTML size and compression, HTTP version, the number and weight of scripts, styles and images, render-blocking resources, caching and modern image formats, and adds Core Web Vitals from PageSpeed Insights when available.

Frequently asked questions