Google's limits at a glance
| Measure | Good | Poor | Used for ranking |
|---|---|---|---|
| LCP | 2.5 s or less | Over 4 s | Yes |
| INP | 200 ms or less | Over 500 ms | Yes |
| CLS | 0.1 or less | Over 0.25 | Yes |
| FCP | 1.8 s or less | Over 3 s | No |
| TTFB | 0.8 s or less | Over 1.8 s | No |
| TBT (mobile lab) | Under 200 ms | Over 600 ms | No |
| Speed Index (mobile lab) | 3.4 s or less | Over 5.8 s | No |
Where each measure falls during a page load
The first three happen in order on every load. Total Blocking Time counts the busy stretches in between, and Interaction to Next Paint keeps measuring for as long as the shopper stays on the page.
Terms
- Core Web Vitals
- Google's three measures of page experience: Largest Contentful Paint, Interaction to Next Paint and Cumulative Layout Shift. Scored from real Chrome visits and used in ranking.
- Largest Contentful Paint (LCP)
- How long the biggest image or text block on the screen takes to show. Good is 2.5 seconds or less; poor is over 4 seconds.
- Interaction to Next Paint (INP)
- How fast the page visibly responds after a tap, click or key press. Good is 200 milliseconds or less; poor is over 500 milliseconds.
- Cumulative Layout Shift (CLS)
- How much the page jumps around while it loads. Good is 0.1 or less; poor is over 0.25.
- First Contentful Paint (FCP)
- When the first text or image appears on screen. Good is 1.8 seconds or less; poor is over 3 seconds. Not a Core Web Vital, but part of the PageSpeed score.
- Time to First Byte (TTFB)
- How long the browser waits for the first byte of the page from the server. Good is 0.8 seconds or less; poor is over 1.8 seconds.
- Total Blocking Time (TBT)
- In the lab test, how long the page was too busy running code to respond. On mobile, under 200 milliseconds is good and over 600 is poor. It is the largest part of the PageSpeed score.
- Speed Index
- In the lab test, how quickly the visible part of the page fills in. On mobile, 3.4 seconds or less is good and over 5.8 seconds is poor.
- PageSpeed Insights
- Google's free tool that reports a page's real-visit Core Web Vitals and runs a lab test with a 0 to 100 score.
- Real-visit data
- Measurements from real Chrome users over the last 28 days, collected in the Chrome UX Report. Google's Core Web Vitals assessment is based on it.
- Lab test
- One simulated page load on a set device and connection. Useful for finding causes; its score changes a little each run.
- Page experience
- Google's name for how a page feels to use beyond its content, including Core Web Vitals, secure connections and not covering content with pop-ups. Its ranking systems take it into account.
- Performance score
- The 0 to 100 number from a PageSpeed Insights lab test. 90 and above is good, 50 to 89 needs improvement, under 50 is poor. Google does not use it for ranking.
- Tag manager
- A tool, such as Google Tag Manager, that loads analytics and ad tags on a site from one place. The tags it loads are what cost speed, not the tool itself.
- Third-party script
- Code from another company that runs on a website, such as chat, analytics, reviews or an ad pixel.
- Lazy loading
- Waiting to load an image until the visitor is about to see it. Right for gallery photos further down; wrong for the first photo.
- Vehicle detail page (VDP)
- The page for one vehicle, with its photos, price, features and lead forms.
- Search results page (SRP)
- The inventory listing page that shows vehicles matching a shopper's search or filters.
Where to go next
Each Core Web Vital has its own guide: Largest Contentful Paint, Interaction to Next Paint and Cumulative Layout Shift. For server response, see Time to First Byte. To see your own numbers, run the free speed test.