Time to First Byte (TTFB) measures the time from when a request starts until the first byte of response is received.
This is different from waiting for the complete HTML download.
Live Demo
Fast Response (No Delay)
TTFB: - ms
Full Load: - ms
Status: Ready
Slow Response (3s Server Delay)
TTFB: - ms
Full Load: - ms
Status: Ready
Navigation Timing API Demo
Real-time Log
Ready to measure TTFB...
Key Points Demonstrated:
TTFB is measured when first byte arrives - not when full content is downloaded
Server processing time directly affects TTFB
Network latency is included in TTFB
Resource size doesn't affect TTFB - only affects full download time