Time To First Byte (TTFB)

A foundational web performance metric measuring the time from when a user makes a request to when their browser receives the very first byte of the HTML response. It is a fundamental measure of server and network responsiveness and is influenced by redirect time, DNS lookup, connection setup (including the TLS handshake), and the server's backend processing time. A slow TTFB creates a bottleneck for every subsequent metric, delaying both FCP and LCP.