Bulk Core Web Vitals: measure 10 pages at once.

What are Core Web Vitals?

Core Web Vitals are the three metrics Google uses to measure a page’s user experience. They are part of the page experience signals; more importantly, a slow, jumpy page drives visitors away.

• LCP (Largest Contentful Paint): how long the largest content element takes to appear. Good: 2.5 seconds or less.
• INP (Interaction to Next Paint): how quickly the page responds when a user clicks or taps. Good: 200 milliseconds or less.
• CLS (Cumulative Layout Shift): how much elements move while the page loads. Good: 0.1 or less.

A page “passes” only if all three are in the good range. Values reflect the experience of 75% of visitors.

What does this tool do?

• Measures up to 10 URLs through the Google PageSpeed Insights API, three at a time in parallel.
• Looks at field data first: the real experience of Chrome users over the last 28 days (Chrome UX Report). If the page lacks enough data, it shows site-wide data; if that is missing too, it shows Lighthouse lab data and says so clearly.
• Mobile and desktop are measured separately; Google ranks on the mobile result.
• All results can be downloaded as CSV.

Field data vs lab data

Field data comes from real visitors and is what Google uses in its assessment. Lab data is a simulation on a single test device at a set connection speed; it is useful for diagnosing problems but does not exactly reflect real experience. Low-traffic pages have no field data; that is normal.

Where to start if results are poor

• High LCP: compress the main image and convert it to WebP/AVIF first, then look at server response time and unnecessary CSS/JS loaded at the top of the page.
• High INP: reduce or delay heavy JavaScript, especially third-party tags such as chat, ads and tracking.
• High CLS: give images and ad slots fixed width and height, and stop late-loading banners from pushing content down.

Limitations

Each measurement can take 10–30 seconds on Google’s side. Up to 10 URLs are checked at a time. Field data updates daily, so results are cached for 6 hours.

Measurements use the Google PageSpeed Insights API and Chrome UX Report data. The idea of measuring many pages in one go was inspired by GitHub user sundios’s open-source SEO-Lighthouse-Multiple-URLs; this tool does not use that project’s code.