Web metrics are a way of measuring [[performance]] for websites. Different metrics are useful for different things, and some are more important for certain use cases than others. Tools like Lighthouse and Calibre are used to measure them.
Some are based on interactivity, others are based on painting. Different parts of the [[rendering]] cycle.
measures the time from when the page starts loading to when any part of the page's content is rendered on the screen.
measures the time from when the page starts loading to when the largest text block or image element is rendered on the screen.
measures the time from when a user first interacts with your site (when they click a link, tap a button, or use a custom, JavaScript-powered control) to the time when the browser is actually able to respond to that interaction. Note, this is being replaced by INP in March 2024
measures the latency of every tap, click, or keyboard interaction made with the page, and—based on the number of interactions—selects the worst interaction latency of the page (or close to the highest) as a single, representative value to describe a page's overall responsiveness.
measures the time from when the page starts loading to when it's visually rendered, its initial scripts (if any) have loaded, and it's capable of reliably responding to user input quickly.
measures the total amount of time between FCP and TTI where the main thread was blocked for long enough to prevent input responsiveness.
measures the cumulative score of all unexpected layout shifts that occur between when the page starts loading and when its lifecycle state changes to hidden.
measures the time it takes for the network to respond to a user request with the first byte of a resource.