Largest Contentful Paint

Largest Contentful Paint records the moment the biggest piece of content in the viewport finishes rendering. On most pages that is the hero image, a background image, a video poster or the headline block. It is the closest single number to the question a visitor is actually asking, which is "has this page loaded yet".

Interaction to Next Paint

Interaction to Next Paint measures how long a page takes to show a visual response after somebody clicks, taps or presses a key. It observes every interaction during the visit and reports close to the worst one, so a single badly handled click can define the score for the whole session.

Cumulative Layout Shift

Cumulative Layout Shift measures how much visible content moves position while the page is loading, without the visitor causing it. Unlike the timing metrics it has no unit. It is a score built from how much of the screen moved and how far it travelled.

First Contentful Paint

First Contentful Paint records when the browser renders the first piece of content from the DOM, whether that is text, an image, a canvas or an SVG. It marks the moment a visitor stops looking at a blank screen and starts believing the page is working.

Time to First Byte

Time to First Byte measures how long it takes from starting the navigation to receiving the first byte of the response. It covers redirects, DNS resolution, the TCP connection, the TLS handshake and the time the server spent producing the page.

Total Blocking Time

Total Blocking Time adds up the portion of every long task that exceeds 50 milliseconds, between First Contentful Paint and the point the page becomes interactive. It quantifies how long the page was visibly present but unable to respond.