High impact · weight 8 · worth up to 3.4 points of the total score
LCP is the moment the biggest element in the viewport finishes rendering, which is when a visitor feels the page has arrived. Google's threshold for good is 2.5 seconds.
Preload the hero image or font, serve images sized for their slot in a modern format, and remove render-blocking CSS.
Check a page for this, and the other 75 checks at once
Cumulative Layout Shift
CLS measures content jumping around after it appears. It is why a visitor taps the wrong button when an ad or a late-loading image pushes the page down under their finger.
Interaction to Next Paint
INP is how long the page takes to visibly respond after a tap or a click. Above 200ms the interface starts to feel like it is ignoring the user. INP replaced First Input Delay (FID) as a Core Web Vital in March 2024.
HTML is compressed in transit
Gzip or Brotli typically cuts HTML to a quarter of its size. Serving it uncompressed wastes that bandwidth on every single request, and it is usually one line of server config.
Time to first byte
How long the server took to start answering, measured on our own request. A slow first byte delays everything downstream no matter how well the front end is built.
