The page speed test loads a web page in a test browser and measures how quickly it appears and becomes usable, on a simulated mid-range phone or on a desktop computer. You get a performance score out of 100, the Core Web Vitals that Google uses as a ranking signal, scores for accessibility, best practices and SEO, and a list of the changes that would speed the page up the most.
The test is run by Google PageSpeed Insights, the same engine (Lighthouse) used in Chrome’s developer tools, so the numbers match what Google reports.
How to test your page speed
- Enter the page address and choose Mobile or Desktop. Start with mobile: most visitors use phones, and Google ranks pages using their mobile version.
- Click “Test speed” and wait 15 to 40 seconds while the page loads in Google’s test browser.
- Read the scores, then work through “What to fix first”, which is sorted by the time each fix could save.
Core Web Vitals explained
Core Web Vitals are three measurements of real-world experience. Google considers a page good when at least 75% of visits meet these targets:
| Metric | What it measures | Good | Poor |
|---|---|---|---|
| Largest Contentful Paint (LCP) | How long the main content takes to appear | 2.5 s or less | Over 4 s |
| Interaction to Next Paint (INP) | How quickly the page responds to taps and clicks | 200 ms or less | Over 500 ms |
| Cumulative Layout Shift (CLS) | How much the layout jumps while loading | 0.1 or less | Over 0.25 |
Real-user data vs lab results
The report has two parts. What real users experience comes from the Chrome User Experience Report: anonymous timings from real Chrome visitors over the last 28 days. It’s what Google uses for rankings, but it only exists for pages and sites with enough traffic, so new sites often see “not enough data”.
The lab test is a single load in a controlled environment. It’s available for every page and is the best way to check whether a change helped, but the score can move a few points between runs because of network and server variation.
How to speed up a page
- Compress and resize images. Images are usually the heaviest part of a page. Serve them at the size they’re displayed, in WebP or AVIF, and lazy-load images below the fold. Our image compressor helps.
- Cut unused JavaScript. Every script must be downloaded and run. Remove plugins and trackers you don’t need, and load the rest with defer.
- Reserve space for images, ads and embeds with width and height attributes, so the layout doesn’t shift as they load.
- Use caching and a CDN so returning visitors and distant visitors get files faster.
- Pick a fast host. If the server takes over half a second to respond, everything else waits.
Frequently asked questions
Why is my mobile score lower than desktop?
The mobile test simulates a mid-range phone on a slower connection, with a slower processor. The same page has to do more work with fewer resources, so mobile scores are almost always lower. That’s also closer to what many real visitors experience.
Why did my score change when I tested again?
Lab results vary slightly with server load, network conditions and ads or third-party scripts that change between loads. Run the test two or three times and look at the typical result rather than a single number.
Does page speed affect Google rankings?
Yes, but modestly. Core Web Vitals are part of Google’s page experience signals. Relevant, helpful content matters far more, but when pages are similar, the faster one has an edge, and speed affects how many visitors stay.
What happens to the address I enter?
It’s sent from your browser to Google’s PageSpeed Insights service, which loads the public page and returns the results. SmartToolsy doesn’t store your tests.
Why does it say there’s no real-user data?
Chrome only publishes real-user timings for pages and sites with enough visitors. Until then, use the lab results, which measure the same things in a test environment.