Suggest an editImprove this articleRefine the answer for “What metrics are used to measure site speed?”. Your changes go to moderation before they’re published.Approval requiredContentWhat you’re changing🇺🇸EN🇺🇦UAPreviewTitle (EN)Short answer (EN)Several key metrics are used to evaluate the speed and "responsiveness" of a site. **Key point:** they show how fast a page loads, when the user sees content, and how soon they can start interacting with the site.Shown above the full answer for quick recall.Answer (EN)ImageSeveral key metrics are used to evaluate the speed and "responsiveness" of a site. They show **how fast a page loads, when the user sees content, and how soon they can start interacting with the site**. Below are the most important and most commonly used ones. --- ## Core Web Vitals (Google's core metrics) This is the main set of metrics that both search engines and developers rely on. ### **LCP (Largest Contentful Paint)** Shows **when the largest visible element on screen appeared** (an image, a banner, a heading). - Good: under **2.5 sec** - Bad: the user sees a blank screen or a skeleton for a long time Put simply: *"How quickly the page appears loaded"* --- ### **INP (Interaction to Next Paint)** Measures **how quickly the site responds to user actions** (a click, typing text). - Good: under **200 ms** - Bad: buttons respond with a delay *"How much the site 'lags' during interaction"* (FID used to be used instead of INP, but it's now considered deprecated.) --- ### **CLS (Cumulative Layout Shift)** Shows **how much content jumps around during loading**. - Good: under **0.1** - Bad: buttons and text shift, and the user clicks the wrong thing *"How stable the page's layout is"* --- ## Page load metrics These help you understand **what exactly happens during loading**. ### **TTFB (Time To First Byte)** The time from the request to receiving the first byte from the server. - Affected by the server, caching, SSR - A good value is under **500 ms** *"How quickly the server responds"* --- ### **FCP (First Contentful Paint)** Shows **when the first content appears on screen** (text, an icon, a background). *"When the user realizes the site has started loading"* --- ### **TTI (Time To Interactive)** The time when the page is **not only visible, but also fully ready for interaction**. *"When the site can actually be used without lag"* --- ## Why these metrics matter - They affect the user's **perception of speed** - They're tied to **SEO and ranking** - They help you understand **exactly where the bottleneck is**: the server, JS, styles, images --- ## In short - **LCP** - how fast the main content appears - **INP** - how quickly the site responds - **CLS** - whether the interface jumps around - **TTFB** - the server's response speed - **FCP / TTI** - the sense of loading starting and the page being readyFor the reviewerNote to the moderator (optional)Visible only to the moderator. Helps review go faster.