Glossary / TTFB

What is TTFB (Time To First Byte)

TTFB (Time To First Byte) is the time from the moment the browser sends a request to the moment it receives the first byte of the server's response. In plain terms, it is how long the site thinks before it starts answering. It is measured in milliseconds, and the lower it is, the sooner the page starts to load.

TTFB covers several stages: the DNS lookup, the connection, the TLS handshake, and above all the time the server needs to build the response. That is why a high TTFB usually points to a slow backend: heavy database queries, no caching, or overloaded hosting.

Search engines and tools like PageSpeed watch TTFB because it sets the floor for speed: until the first byte arrives, the browser cannot start drawing the page. A good target is under 200 ms, acceptable is under 500 ms, and above 800 ms the delay is noticeable.

You lower TTFB with page caching, a faster server, a CDN closer to the visitor, and cleaner code and queries. A distant server adds latency too, because the signal physically travels longer.

Example

TTFB: 180 ms

Common mistakes

• Confusing TTFB with the full page load time - it is only the time to the first byte, not to a finished page.
• Assuming hosting is always to blame, when heavy site code or slow database queries often cause a high TTFB.
• Ignoring geography: a server on the other side of the world adds TTFB even on a fast site.
• Measuring TTFB once, when the number fluctuates and you need several readings, with and without cache.

Related terms

• CDN What is a CDN (Content Delivery Network)
• HTTP/2 What is HTTP/2
• HTTP/3 What is HTTP/3
• gzip / Brotli What is gzip and Brotli compression
• DNSBL What is a DNSBL (blacklist)