What is Time to First Byte (TTFB)?

Time to First Byte (TTFB) measures how long the browser waits after asking for your page before the server sends back the first byte of it. It is your hosting and server’s reaction time, before anything is even drawn:

• Good is under 0.8 seconds - Google’s threshold for a responsive server.
• It sits underneath every other metric - a slow TTFB delays FCP, which delays LCP, so nothing downstream can be fast.
• The usual causes - cheap or overloaded shared hosting, a server far from your visitors, or a slow database and unoptimised plugins.

TTFB is the one metric you mostly fix with infrastructure rather than code - better hosting, caching, or a CDN. If your TTFB is high, no amount of image-tweaking will make the page feel fast; start with the server.