Website Speed Test
Run a complete website speed test online and get everything in one report. It is a free online tool. There is no install and no signup. It runs right in your browser.
Enter any URL and you get a lot back. You see Core Web Vitals with a real-user pass or fail verdict. You get a full Lighthouse audit for Performance, Accessibility, Best Practices and SEO. You also see connection timing, a request waterfall and a page-weight breakdown. A load filmstrip shows how the page paints. A prioritised list tells you what to fix first. One DiagnoSEO Grade sums it all up at a glance.
What does the "Website Speed Test" tool do?
The tool runs a single performance test of the page you enter. It measures the full server timing. That covers DNS lookup, TCP connection, TLS handshake, time to first byte and download. It also parses the HTML and lists every resource. Then it weighs the page in parallel. So you can see where the bytes and requests really go. You get a request waterfall, a content breakdown by type and domain, and a response-code summary. You can export the whole run as a HAR file.
On top of that, it can pull real Core Web Vitals. That means LCP, INP and CLS. You see the field distribution and a clear pass or fail verdict. You can switch between this URL and the whole origin. It also adds a full Lighthouse audit across four categories. You get lab metrics like FCP, TTFB, TBT and Speed Index. A load filmstrip and a final screenshot show the render. Concrete optimisation opportunities round it out. Everything is summed up in one DiagnoSEO Grade from A to F.
Most of the analysis runs without any external API. So a test returns in seconds. It is never blocked by usage quotas. You can add a free PageSpeed Insights key. That unlocks the full real-user and Lighthouse layer at no cost.
How does the Website Speed Test help SEO specialists and website owners?
Page speed and Core Web Vitals are part of Google's page experience signals. Slow pages also lose conversions. This tool turns a vague "your site is slow" into a clear, prioritised to-do list.
Every issue is ranked by severity. Each one is explained in plain language, with evidence from your page. On paid plans you also get ready-to-deploy fixes. That is copy-paste code showing the change from before to after. It is tailored to your server and CMS.
Typical uses of the Website Speed Test tool
- Check whether a page passes Core Web Vitals (LCP, INP, CLS) for real users.
- Audit Performance, Accessibility, Best Practices and SEO in one run.
- Find render-blocking CSS and JavaScript that delay the first paint.
- Inspect the request waterfall to spot slow, blocking or oversized resources.
- See the full page weight and which resource types and domains dominate it.
- Diagnose a slow server response time (TTFB).
- Verify compression, caching, HTTP/2-3 and HTTPS configuration.
- Test the page as rendered from a specific country via premium proxy.
- Generate ready-to-deploy fixes for the detected issues.
Comparison of the "Website Speed Test" tool with other tools
| Functionality | DiagnoSEO | Other tools |
|---|---|---|
| Instant test without API quotas | ✅ | ❌ |
| Core Web Vitals (field + lab data) | ✅ | ✅ |
| Full Lighthouse audit (Performance, Accessibility, SEO) | ✅ | ✅ |
| Everything in a single report (no juggling tools) | ✅ | ❌ |
| Full connection timing breakdown | ✅ | ❌ |
| Ready-to-deploy fixes (before → after code) | ✅ | ❌ |
| Choose the country the test runs from | ✅ | ❌ |
| JavaScript-rendered resource inventory | ✅ | ❌ |
Tips and good practices
- Fix the highest-severity issues first. They usually move the score the most.
- Test both mobile and desktop. Google indexes mobile first.
- Compare field data from real users with lab data. Field data is what counts for ranking.
- Re-test after each change to confirm the improvement.
- Keep your largest above-the-fold image out of lazy loading. That keeps LCP fast.
Most common mistakes
- Chasing a perfect lab score while real-user field data stays red.
- Lazy-loading the LCP image, which delays the largest paint.
- Shipping uncompressed, unminified CSS and JavaScript.
- Leaving images without width and height, which causes layout shifts (CLS).
- Serving static assets with no cache policy.
How to use the Website Speed Test tool
- Paste the URL you want to test.
- Choose the device: mobile, desktop, or both.
- Optionally open advanced settings to test through a premium proxy from a chosen country.
- Run the test and read the performance score and Core Web Vitals.
- Work through the prioritised opportunities.
- On a paid plan, generate ready-to-deploy fixes and apply the code.
Case study
A content site scored well in the lab but failed Core Web Vitals in Search Console. The test found a 1.6 second server response time. It also flagged twelve render-blocking scripts.
The owner enabled server caching and deferred non-critical JavaScript. TTFB then dropped below 400 ms. The page started passing Core Web Vitals for real users.
FAQ
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Yes. When real-user field data is available, it shows LCP, INP and CLS. You see the split across good, needs-work and poor, plus a pass or fail verdict. If field data is missing, the tool reports lab values and a server-side estimate.
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It is a single grade from A to F. It blends the performance score (70%) with a structure score (30%) from the Lighthouse audits. So you can judge a page at a glance, much like a GTmetrix grade.
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Yes. The timing breakdown, page weight, resource inventory and recommendations all run server-side. None of that needs an external API. You can add a free PageSpeed key to also include Lighthouse data.
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For each detected issue, paid plans generate copy-paste code. It shows the change from before to after. Examples include server config for compression and caching, or HTML rewrites for images.
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Yes. In advanced settings you can load the page through a premium proxy. You pick the country it runs from. This helps when a site serves different content or speed by region.
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It is a single, on-demand performance test. Run it whenever you want a fresh snapshot of a page's speed.