Guide
What the website speed test measures and how to read it
The test combines two sources: a lab test that runs right now, and data from real Chrome users over the last 28 days. Google mainly looks at the second one.
Core Web Vitals
Three metrics Google uses to measure page experience. Good means at least 75% of visits hit these values:
- LCP of 2.5 s or less: the main content appears.
- INP of 200 ms or less: the page responds to a click or typing.
- CLS of 0.1 or less: content doesn't jump around while loading.
Scores from 0 to 100
The Lighthouse score sums up the lab test. 90 or above is good, 50 to 89 needs improvement, and below 50 is poor. The mobile test simulates a slower phone and network, so it scores lower than desktop.
Why speed matters
A slow page turns visitors away before they even see your offer. Core Web Vitals are also among the signals Google uses to rank pages in search.
What slows websites down most
- Large images in older formats instead of WebP or AVIF.
- Dozens of plugins and scripts that load on every page.
- Slow hosting or no caching.
- Third-party analytics and ad scripts.
- Web fonts that aren't preloaded.