AI search glossary
Core Web Vitals
Core Web Vitals are Google’s three measurements of real-user page experience: Largest Contentful Paint for loading, Interaction to Next Paint for responsiveness, and Cumulative Layout Shift for visual stability. Core Web Vitals are assessed at the 75th percentile of real page loads, not in a lab test.
What are the current thresholds?
Three metrics, three bands each, measured at the 75th percentile of real page loads and segmented across mobile and desktop. Interaction to Next Paint replaced First Input Delay as a stable Core Web Vital in 2024, so any guide still listing FID is out of date.
| Metric | Good | Poor |
|---|---|---|
| Largest Contentful Paint | 2.5 seconds or less | over 4.0 seconds |
| Interaction to Next Paint | 200 ms or less | over 500 ms |
| Cumulative Layout Shift | 0.1 or less | over 0.25 |
How much do Core Web Vitals affect rankings?
Less than the attention they get, and the honest shape is asymmetric. Moving a page out of the poor band can matter in a close contest; polishing a page that is already good measures close to nothing. Sites without enough real-user data in Google’s dataset get no page-experience signal at all, which quietly exempts most small sites from the whole discussion. The measurement itself is often misread as well. These are field metrics from real visitors over a rolling window, not a laboratory score, so a synthetic test result is a diagnostic rather than the number Google uses.
A page can score badly in a lab tool and pass in the field, and the reverse happens too. The gap is usually caching and device mix: a lab test runs cold on one simulated phone, while your real visitors arrive with warm caches on a range of hardware. Both numbers are worth having for different jobs: the lab result tells you what changed after a deploy, and the field data tells you what your visitors actually experienced.
Do Core Web Vitals affect AI citations?
There is no evidence that they do, and there is a mechanism suggesting they mostly cannot. AI crawlers fetch HTML and do not render it: Vercel’s network analysis found the major AI crawlers requesting JavaScript and executing none of it. Layout shift and interaction latency are properties of a rendered page that no AI crawler ever produces.
What survives is the underlying reason to care. A page slow enough to time out a fetch is a page that does not get collected, and the JavaScript you do not ship cannot break either your interaction score or your visibility. Speed is worth pursuing for users and for revenue, and claiming a citation benefit for it is inventing one.
Related terms
- Server-Side Rendering (SSR)Server-side rendering means a page’s HTML arrives from the server already containing its content, rather than being assembled in the browser by JavaScript.
- AI CrawlerAn AI crawler is an automated fetcher run by an AI company to collect web pages.
- SERPA SERP is a search engine results page: everything an engine returns for a query, including the organic links, the ads and the features above and between them.
- Crawl BudgetCrawl budget is the amount of crawling an engine will do on a site, set by what the server can take and by how much the engine wants the content.
This definition of Core Web Vitals was checked against the following sources. Definitions are reviewed quarterly and edited only when they are wrong, so the reviewed date above moves on a real correction and not on a schedule.
- Google web.dev: Web Vitals, with current thresholds and percentile, read 18 August 2026
- Vercel: the rise of the AI crawler, 17 December 2024, read 18 August 2026
Every entry is listed on the RankX AI glossary index, and this page is available as Markdown at /glossary/core-web-vitals.md.
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