TTFB
Time to First Byte
ELI5 — The Vibe Check
How long it takes from clicking a link to receiving the very first byte of data from the server. It measures your server's speed — how fast it can start sending a response. A slow TTFB means your server is thinking too hard, your database is choking, or your CDN is taking a vacation.
Real Talk
Time to First Byte measures the duration from the client's HTTP request to receiving the first byte of the response. It encompasses DNS lookup, TCP connection, TLS handshake, and server processing time. Google considers TTFB under 800ms acceptable; under 200ms is good.
When You'll Hear This
"Our TTFB is 2 seconds — the server is way too slow." / "Adding a CDN dropped our TTFB from 800ms to 50ms."
Related Terms
CDN (Content Delivery Network)
A CDN is a network of servers spread around the world that store copies of your files.
Latency
Latency is the delay before data starts moving — the time it takes for a request to go from your device to the server and back.
Web Vitals
Web Vitals are Google's report card for how good your website feels to use. They measure things like 'how fast does the main content load?