What is TTFB?
TL;DR
TTFB (Time to First Byte) measures the time between a browser or crawler requesting a page and receiving the first byte of the response from the server.
Last updated: 2026-03-09
Definition#
Time to First Byte (TTFB) measures the time from when a client (browser or crawler) sends an HTTP request to when it receives the first byte of the response. It includes DNS lookup, TCP connection, TLS handshake, and server processing time.
A good TTFB is under 200 milliseconds. Between 200 and 500 milliseconds is acceptable. Over 500 milliseconds indicates a slow server that may cause problems for crawlers.
Common causes of slow TTFB include shared hosting with limited resources, heavy server-side processing (complex database queries, unoptimized CMS), lack of server-side caching, and geographic distance between the server and the crawler.
Why It Matters for AI Readiness#
TTFB directly affects how many pages a crawler can fetch in a given time. AI crawlers request many pages sequentially. If each request takes 500ms longer than necessary, the crawler processes far fewer of your pages. The Speed & Performance factor considers TTFB.
Improve TTFB with better hosting, server-side caching, and a CDN. See How to Improve Page Speed.
Related Concepts#
TTFB is the first step in the loading timeline, followed by FCP and then LCP. It affects all Core Web Vitals because a slow server delays everything.
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