What is page speed?
A plain-English explanation of what page speed means, how it is measured, and why different tools give different scores.
"Page speed" sounds simple — it is how fast your page loads. But in practice it is more nuanced than a single number. This guide breaks down what speed actually means and why different tools measure it differently.
Quick summary
Page speed is not one number — it is several measurements that together describe how fast your page feels to a visitor. The most important measurements are about when content first appears, when it becomes usable, and whether it moves around unexpectedly.
What "loading" actually means
When a visitor opens your website, several things happen in a sequence:
- Their browser sends a request to your server
- The server sends back the HTML file (the page's structure)
- The browser starts reading that file and discovers it needs images, stylesheets, and scripts
- The browser fetches all of those files
- The browser puts everything together and displays the final page
"Page speed" describes how long different stages of this process take. A page can feel fast even if it takes three seconds to fully finish loading — as long as the most important content appears quickly.
The key speed measurements
Rather than one score, modern speed tools measure several things:
| Measurement | What it means | Good target |
|---|---|---|
| First Contentful Paint (FCP) | When the first text or image appears | Under 1.8 seconds |
| Largest Contentful Paint (LCP) | When the main content loads | Under 2.5 seconds |
| Interaction to Next Paint (INP) | How quickly the page responds to clicks/taps | Under 200 milliseconds |
| Cumulative Layout Shift (CLS) | How much the layout jumps around as it loads | Under 0.1 |
| Time to First Byte (TTFB) | How long before your browser receives anything | Under 800 milliseconds |
The three most important — LCP, INP, and CLS — are Google's Core Web Vitals. They are the measurements Google uses as a ranking signal.
Why different tools give different scores
You may have checked your speed with two different tools and gotten very different results. This is normal.
Different tools measure speed in different ways:
- Lab tests (like Lighthouse) load your page in a controlled environment. They are consistent but may not match real-world experience.
- Field data (like Chrome User Experience Report) collects real measurements from real visitors. This reflects actual experience but varies by location, device, and connection.
Also, scores are relative to other sites. What counts as "fast" changes over time as the web improves.
Which tool should you use?
Google PageSpeed Insights is the most useful starting point — it combines both lab and field data and links directly to the factors Google uses for ranking. See How to measure your site's speed for a full guide.
The difference between server speed and page speed
These are related but not the same thing:
Server speed (Time to First Byte) is how fast your hosting sends the first response. This is largely about your hosting environment.
Page speed is the full experience, including all the images, scripts, fonts, and other files the page needs. You can have a fast server but a slow page if the page is poorly optimized.
Why "100/100" is not always the goal
Tools like PageSpeed Insights give a score out of 100. A perfect score is impressive — but it is not the only goal, and chasing a perfect score sometimes means making compromises (like removing features your visitors value).
A more useful question: "Are my Core Web Vitals in the green zone?" and "Is my site faster than my main competitors?" Read more in Performance: realistic expectations.
Common questions
Related guides
- Core Web Vitals explained
- How to measure your site's speed
- Why website speed matters
- What slows websites down
- Performance terms, explained simply
Need a hand?
Learn more
Why website speed matters
How a slow website affects your visitors, your sales, and your position on Google — and why speed is worth investing in.
Core Web Vitals explained
Google's three key speed measurements explained in plain English — what they measure, what the targets are, and why they matter for your site.