Core Web Vitals:

The Core Web Vitals report shows URL performance grouped by status (Poor, Need improvement, Good), metric type (CLS, FID, INP, and LCP), and URL group (groups of similar web pages).

The report is based on four metrics as measured by actual user data: LCP, FID, INP, and CLS. Once a URL group has a threshold amount of data for both LCP and CLS, the URL group's status is its most poorly performing metric. So, for example, if a URL group has poor CLS but good FID, the URL status is "poor."

If a URL group does not have a minimum amount of reporting data for both LCP and CLS, the URL is omitted from the report.

Only indexed URLs can appear in this report. Data is assigned to the actual URL, not the canonical URL, as it is in most other reports).

Remember that data is combined for all requests from all locations. If you have a substantial amount of traffic from a country with, say, slow internet connections, then your performance in general will go down. You can break down your performance by country using BigQuery if you suspect this might be a cause for low performance.

Group status: Poor, Need improvement, Good

The labels Poor, Need improvement, and Good are applied to a URL group for that specific device type. A URL group without threshold data for both LCP and CLS will not be on the report (for example, if the URL only has threshold data for LCP but not CLS, it won't be shown).

The status for a URL group defaults to the slowest status assigned to it for that device type. For example,

• A URL on mobile with Poor CLS but Need improvement LCP is labeled Poor on mobile.

• A URL on mobile with Need improvement LCP but Good CLS is labeled Need improvement on mobile.

• A URL with Good FID, LCP, INP, and CLS on mobile and Need improvement FID, LCP, INP, and CLS on desktop is Good on mobile and Need improvement on desktop.

Status definitions

Here are the performance ranges for each status:

• LCP (largest contentful paint): The amount of time to render the largest content element visible in the viewport, from when the user requests the URL. The largest element is typically an image or video, or perhaps a large block-level text element. This metric is important because it indicates how quickly a visitor sees that the URL is actually loading.

  • Group LCP shown in the report is the time it takes for 75% of the visits to a URL in the group to reach the LCP state.

• FID (first input delay): The time from when a user first interacts with your page (when they clicked a link, tapped on a button, and so on) to the time when the browser responds to that interaction. This measurement is taken from whatever interactive element that the user first clicks. This is important on pages where the user needs to do something, because this is the delay before the page becomes interactive.

  • Group FID shown in the report means that 75% of visits to a URL in this group had this value or better.

• INP (interaction to next paint): A metric that assesses a page's overall responsiveness to user interactions by observing the time that it takes for the page to respond to all click, tap, and keyboard interactions that occur throughout the lifespan of a user's visit to a page. The final INP value is the longest interaction observed, ignoring outliers.

  • Group INP shown in the report means that 75% of visits to a URL in this group had this value or better.

• CLS (Cumulative Layout Shift): CLS measures the sum total of all individual layout shift scores for every unexpected layout shift that occurs during the entire lifespan of the page. The score is zero to any positive number, where zero means no shifting and the larger the number, the more layout shift on the page. This is important because having pages elements shift while a user is trying to interact with it is a bad user experience. If you can't seem to find the reason for a high value, try interacting with the page to see how that affects the score.

  • Group CLS shown in the report is the lowest common CLS for 75% of visits to a URL in the group.