Time to First Byte (TTFB)
01 Definition
Time to First Byte (TTFB) meaning: TTFB measures how long the browser waits for the first byte from the server.
Time to First Byte measures the delay between a browser requesting a page and receiving the first byte of the response. It reflects server speed, hosting, and network time. A high TTFB delays everything that follows, so it is often the first thing to check when a page loads slowly.
Why it matters
How Time to First Byte (TTFB) fits the work
TTFB reflects how fast your server responds, and because it comes first, cutting it can improve every later loading metric.
In context
Adding page caching cut the site's Time to First Byte from 900 milliseconds to 200 milliseconds, speeding up the rest of the load.
Practical note
TTFB is a diagnostic, not a Core Web Vital. Caching, a content delivery network, and faster server code are common ways to reduce it.