TL;DR
Time to First Byte (TTFB) is the duration between the browser requesting a page and receiving the first byte of the HTML response, including DNS lookup, connection setup, server processing, and network transfer.
What is Time to First Byte (TTFB)?
Time to First Byte (TTFB) is the duration between the browser requesting a page and receiving the first byte of the HTML response, including DNS lookup, connection setup, server processing, and network transfer.
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TTFB Thresholds & Benchmarks
| Metric | Good | Needs Improvement | Poor |
|---|---|---|---|
| TTFB | ≤ 0.8 s | 0.8 s, 1.8 s | > 1.8 s |
How TTFB is Measured
TTFB is reported by the Navigation Timing API and visible in PageSpeed Insights, WebPageTest, Chrome DevTools, and most real-user monitoring tools.