How to check Core Web Vitals in Claude
Add Caybl.ai from Claude’s connector directory, then ask which pages are slow. Claude reads real-user Core Web Vitals and runs PageSpeed Insights audits for you. No Google API key needed. Part of Pro in your own AI.
- Pro in Claude, free to try in Caybl
- No API key
- ~2 minute setup
No access to custom connectors at work? You can ask the same questions inside Caybl.ai - no setup.
Steps
Sign in to Caybl.ai
Create a free account, then upgrade to Pro to use page speed in Claude. It's built in; there's nothing to connect.
Ask
“Does our site pass Core Web Vitals on mobile?”
Field data and lab data
Google has two kinds of page speed data, and Claude uses both. Field data comes from the Chrome UX Report: what real Chrome users experienced on your page over the last 28 days. It’s what Google uses in search ranking, and Claude can look it up for ten pages in about a second. Lab data comes from a live Lighthouse test, the same one PageSpeed Insights runs. It takes 10-30 seconds and varies a little between runs, but it shows why a page is slow and how much each fix would save.
A good way to ask is in that order: find the pages that are slow for real visitors, then audit those.
What you can ask
- Check“Does our site pass Core Web Vitals on mobile and desktop?”
- Prioritise“Take our top 10 landing pages from Google Analytics. Which are slow for real visitors?”
- Fix“Audit the slowest one and rank the fixes by time saved.”
- Trend“When did our LCP get worse? Did conversions drop the same week?”
- Compare“How do our Core Web Vitals compare with these two competitors?”
“Take our top landing pages from Google Analytics and tell me which ones fail Core Web Vitals.”
“3 of your top 10 fail on mobile, all on LCP, and they get 21% of your sessions. Resizing the product page hero images is the biggest single fix, at about 1.4 s per page.”
Illustrative example - not real account data.
The Google Analytics part needs Google Analytics connected too, which is free. More on what’s included on the PageSpeed Insights MCP server page, including two ready-made Claude skills.
Check your Core Web Vitals in Claude
Part of Pro in Claude and ChatGPT. No API key, nothing to install.
Get started free →FAQ
Yes, with a connector. Claude can't measure page speed on its own, but with Caybl.ai connected it can look up a page's real-user Core Web Vitals from Google's Chrome UX Report and run a live PageSpeed Insights audit. It needs no API key. In Claude and ChatGPT it's part of Pro; on the free plan you can ask the same questions in Caybl's built-in assistant using credits.
The field data: what real Chrome users experienced over the last 28 days, at the 75th percentile. A page passes when LCP is 2.5 s or less, INP is 200 ms or less, and CLS is 0.1 or less. The Lighthouse score is a lab test that helps you find causes; it isn't what Google ranks on.
The Chrome UX Report only publishes numbers for pages and sites with enough Chrome traffic. For a quieter page, Claude falls back to the whole site's numbers and says so, or uses the lab audit alone.
Yes. Both the real-user data and the audits work for any public page, so you can ask Claude to compare your pages with a competitor's.
Up to 100 live audits a day per account, because each one takes Google 10-30 seconds. Real-user Core Web Vitals lookups have no daily limit.
Sources
- Core Web Vitals thresholds - web.dev, Google
- PageSpeed Insights API v5 and Chrome UX Report API - Google for Developers
- Model Context Protocol (MCP) - the open standard Claude uses for connectors