Website Speed Test
Test any page on mobile or desktop. See the Core Web Vitals real Chrome visitors experienced, next to the Lighthouse lab score, with the fixes sorted by how much time each would save.
Short answer
A website speed test measures how long a page takes to become visible and usable. This one runs Google PageSpeed Insights and shows field data, the Core Web Vitals real Chrome users experienced over 28 days, which Google ranks on, and a Lighthouse lab score from one simulated load, useful for debugging. A page passes when LCP is under 2.5 seconds, INP under 200 milliseconds and CLS under 0.1.
Field data and lab data are not the same test
Most confusion about page speed comes from treating the two halves of a PageSpeed report as one number. They answer different questions, and only one of them is a ranking signal.
| Field data (Chrome UX Report) | Lab data (Lighthouse) | |
|---|---|---|
| Source | Real Chrome visitors | One simulated load on Google's servers |
| Time window | Rolling 28 days | Right now |
| Used for rankings | Yes, as Core Web Vitals | No |
| Changes after a fix | Gradually, over four weeks | Immediately |
| Available for | Pages and sites with enough traffic | Any public URL |
| Best for | Knowing whether you have a problem | Finding what causes it |
That is why this tool shows real-visitor data first. A page scoring 45 in the lab can pass Core Web Vitals comfortably, because real visitors on fast devices and cached connections see something the simulated mid-range phone does not.
The Core Web Vitals thresholds
Each of the Core Web Vitals is judged at the 75th percentile of visits, so three in four visitors need a good experience for the page to pass. The wider set of page speed metrics helps diagnose a failure but does not decide it.
| Metric | Measures | Good | Poor |
|---|---|---|---|
| Largest Contentful Paint (LCP) | When the main content appears | 2.5 s or less | Over 4 s |
| Interaction to Next Paint (INP) | How fast the page responds to input | 200 ms or less | Over 500 ms |
| Cumulative Layout Shift (CLS) | How much the layout jumps | 0.1 or less | Over 0.25 |
- LCP is usually an image. A hero image that is too large, lazy-loaded when it should not be, or discovered late by the browser.
- INP is usually JavaScript. Long tasks from analytics, tag managers and chat widgets that keep the main thread busy when a visitor taps.
- CLS is usually missing dimensions. Images, embeds and ad slots without a reserved size, and web fonts that swap in late.
How to test and improve page speed
Five steps, in the order that wastes the least effort.
- 01
Test on mobile first
Google indexes and ranks the mobile version of a page, and the mobile test simulates a mid-range phone on a slower connection. A page that passes on desktop and fails on mobile is failing where it counts.
- 02
Read the real-visitor data before the score
The Core Web Vitals block comes from the Chrome UX Report: what actual Chrome users experienced over the last 28 days. That is what Google uses as a ranking signal. The 0 to 100 score is a lab simulation and is not.
- 03
Find the one metric that fails
Core Web Vitals pass only when Largest Contentful Paint, Interaction to Next Paint and Cumulative Layout Shift are all good at the 75th percentile. Usually one of the three is the problem. Fix that one before anything else.
- 04
Work down the fix list
The fixes are sorted by the time Lighthouse estimates each would save. Image sizing, render-blocking scripts and server response time are the usual top three, and between them they move most pages.
- 05
Re-test, then wait for the field data
The lab score changes the moment you deploy. The real-visitor data is a 28-day rolling window, so a fix takes up to four weeks to show fully in Core Web Vitals and in Search Console.
Server response time affects crawling too
A slow server response delays every metric after it, and it also lowers how fast Google crawls the site. To compare response times across many URLs at once, use the bulk HTTP status code checker, which times every response it fetches.
What this speed test reports
Real-visitor Core Web Vitals
LCP, INP and CLS from the Chrome UX Report, with a pass or fail
Page or site-wide data
Labelled clearly when a page falls back to its site's data
Lighthouse performance score
The 0 to 100 lab score, on mobile or desktop
Lab metrics
First Contentful Paint, LCP, Total Blocking Time, CLS and Speed Index
Fixes sorted by time saved
The top eight opportunities, largest estimated saving first
Server response and page weight
The two numbers that most often explain a slow LCP
What this reads, and what it cannot
Frequently asked questions
What does this website speed test measure?
It runs Google PageSpeed Insights on the URL. You get two things: field data from the Chrome UX Report, which is how fast the page was for real Chrome users over the last 28 days, and a Lighthouse lab test, which loads the page once on a simulated device and scores it from 0 to 100.
What are Core Web Vitals?
Three metrics Google uses to measure page experience: Largest Contentful Paint, how long the main content takes to appear; Interaction to Next Paint, how quickly the page responds to taps and clicks; and Cumulative Layout Shift, how much the layout jumps while loading. They are measured on real visitors, not in a lab.
What are good Core Web Vitals scores?
Largest Contentful Paint at or under 2.5 seconds, Interaction to Next Paint at or under 200 milliseconds, and Cumulative Layout Shift at or under 0.1, each measured at the 75th percentile of visits. A page passes only when all three are good.
Why is the Lighthouse score different every time I run it?
Because it is a single simulated load, and network timing, server load and third-party scripts vary between runs. A swing of a few points is normal. Compare scores across several runs, and trust the real-visitor data for decisions, because it averages thousands of visits.
Does page speed affect SEO rankings?
Yes, but modestly. Core Web Vitals are part of Google's page experience signals, and Google has said they act more as a tie-breaker than a primary factor: relevant content still wins. Speed affects conversions and bounce rate far more directly than it affects rankings.
Why does my page have no real-visitor data?
The Chrome UX Report only includes pages and sites with enough Chrome traffic to be statistically meaningful. A low-traffic page falls back to data for the whole site; a low-traffic site has none at all. In that case only the lab test is available, and Google's ranking signal has nothing to measure either.
Should I test mobile or desktop?
Mobile first. Google uses mobile-first indexing, so the mobile version is the one it evaluates, and mobile is where most pages fail because the test simulates a slower phone and connection. Run desktop afterwards to see how much of the problem is device-specific.
Is this the same as Google PageSpeed Insights?
It uses the same API and the same data. What changes is the presentation: real-visitor data is shown before the lab score, a page that fell back to site-wide data is labelled as such, and the fixes are sorted by estimated time saved so the first row is the one to start with.
How long does the test take?
Usually 20 to 40 seconds, because Lighthouse loads the full page on a simulated device and waits for it to settle. Heavy pages take longer. If a test fails, the page may be blocking Google's servers or behind a login.
What is a good Lighthouse performance score?
90 to 100 is good, 50 to 89 needs improvement and under 50 is poor. On mobile, few real-world pages with ads, analytics and chat widgets score above 90, so treat the score as a direction rather than a target, and judge success by the Core Web Vitals.
Why is my server response time flagged?
Lighthouse flags a server response over 600 milliseconds. Slow responses delay everything after them, including Largest Contentful Paint, and they lower the rate at which Google is willing to crawl the site. Caching, a CDN and faster database queries are the usual fixes.
How long until fixes show up in Search Console?
Up to 28 days. The real-visitor data is a rolling 28-day window, so a fix deployed today is diluted by three and a half weeks of older visits. The lab score changes immediately, which is useful for confirming the fix works before the field data catches up.
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Read guideTerms this tool checks
- Core Web Vitals
Core Web Vitals are a set of specific page experience metrics that Google uses as ranking signals: LCP (Largest Contentful Paint) measuring loading speed, INP (Interaction to Next Paint) measuring interactivity, and CLS (Cumulative Layout Shift) measuring visual stability.
- Page Speed
Page speed refers to how quickly a web page loads and becomes interactive, encompassing metrics like TTFB (Time to First Byte), FCP, LCP, and total load time.
- Crawl Budget
Crawl budget is the number of pages a search engine will crawl on your site within a given timeframe, determined by crawl rate limit (how fast Googlebot can crawl without overloading your server) and crawl demand (how much Google wants to crawl based on popularity and freshness).
One slow page tells you about one template
Speed problems live in templates, and the template that matters is the one behind your most-visited pages. CrawlRaven joins your crawl to Search Console and GA4, so slow pages come back ranked by the traffic they are costing you.