What is page speed?
Page speed is how fast a page loads and becomes usable for a visitor. It is not one number. A page can deliver its first byte quickly and still take seconds to show its main image, or appear quickly and then freeze when tapped. That is why speed is measured with several metrics, each capturing a different moment.
Google has used speed as a ranking signal for desktop since 2010 and mobile since 2018 (the "Speed Update"). Since 2021 the main way it evaluates speed is through Core Web Vitals as part of page experience signals. Speed matters more for users than rankings: slow pages lose visitors before they see anything.
How it works
The metrics that matter most:
- Time to First Byte: how long until the server starts responding.
- First Contentful Paint (FCP): when anything first appears.
- Largest Contentful Paint: when the main content appears.
- Interaction to Next Paint: how quickly the page responds to input.
- Cumulative Layout Shift: how much the layout jumps around.
There are two kinds of data. Lab data comes from a single simulated test, such as Lighthouse. It is repeatable and good for debugging. Field data comes from real Chrome users through the Chrome User Experience Report (CrUX), and it is what Google uses for page experience. PageSpeed Insights shows both, and they often disagree.
Example
A PageSpeed Insights report might show a Lighthouse performance score of 58 on mobile, while the field data section says the page passes Core Web Vitals. The lab test simulates a slow phone on a throttled network; real visitors have faster devices. Use the field data to decide whether there is a problem and the lab diagnostics to find causes, such as an oversized hero image or render-blocking scripts.
In WordPress
The usual causes of slow WordPress sites are slow hosting, no page caching, heavy themes and page builders, too many plugins loading scripts on every page, and unoptimized images. Page caching, a CDN, image compression and modern formats, and removing unused plugins cover most of it. Hydrogen SEO adds no front-end JavaScript, and the hydrogenseo.com platform has a web vitals checker at /seo/web-vitals; see bulk audit and SEO tools.
Common mistakes
- Chasing a Lighthouse score of 100 instead of real-user metrics.
- Testing only the home page when templates like product or post pages are slower.
- Stacking optimization plugins that conflict with each other.
Common questions
Is page speed a ranking factor?
Yes, through Core Web Vitals and page experience, but it is a modest one. Relevance and content quality matter more; speed can break ties and strongly affects user behavior.
What is a good PageSpeed Insights score?
The score is a lab estimate. Focus on whether field data passes Core Web Vitals: LCP within 2.5 seconds, INP within 200 milliseconds, and CLS at 0.1 or less.