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TTFB (Time to First Byte)

/taɪm tə fɜːrst baɪt/abbr.

Filed underPerformanceInfrastructureSEO

In brief · quick answer

TTFB measures the time from navigation request until the first byte of the server response arrives. Target: under 800 ms.

§ 1 Definition

TTFB is a connection-level metric reflecting DNS, TCP/TLS handshake, server processing, and network latency. While not a Core Web Vital itself, it is critical because every millisecond of TTFB directly pushes LCP and FCP later.

§ 2 What Contributes

Redirects, DNS lookup, TCP connection, TLS negotiation, and server response generation. On a fast CDN-cached page, TTFB should be under 200 ms.

§ 3 Common Misunderstandings

Not just server time. Network distance adds base latency (Singapore to London = 150+ ms). Includes redirect hops. Lab TTFB often misses redirect costs.

§ 4 Optimization

Use a CDN with edge caching. Implement full-page caching. Optimize backend queries. Use in-memory caching (Redis). Eliminate unnecessary redirects. Preconnect to origins.

§ 5 Note

Diagnostic metric. Google suggests 800 ms as reasonable. Aim for under 200 ms for competitive performance.

§ 6 In code

<link rel="preconnect" href="https://cdn.example.com">
# Server-Timing: db;dur=53, cache;dur=22, render;dur=89

§ 7 Common questions

Q. Does a CDN always improve TTFB?: A. Yes for static cached content. For dynamic content, the CDN adds a network hop to origin.

§ 8 Thresholds

Rating	TTFB Threshold
Good	≤ 800 ms
Needs Improvement	800 ms - 1.8 s
Poor	> 1.8 s

Key takeaways

Time until first byte of response.
Target: ≤ 800 ms (under 200 ms excellent).
Not a CWV but gates LCP and FCP.
Includes redirects, DNS, TCP/TLS, server processing.

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# TTFB (Time to First Byte)

TTFB measures the time from navigation request until the first byte of the server response arrives. Target: under 800 ms.

Category: Performance (also: Infrastructure, SEO)

Author: Atomic Glue Performance Team

## Definition

## What Contributes

Redirects, DNS lookup, TCP connection, TLS negotiation, and server response generation. On a fast CDN-cached page, TTFB should be under 200 ms.

## Common Misunderstandings

Not just server time. Network distance adds base latency (Singapore to London = 150+ ms). Includes redirect hops. Lab TTFB often misses redirect costs.

## Optimization

Use a CDN with edge caching. Implement full-page caching. Optimize backend queries. Use in-memory caching (Redis). Eliminate unnecessary redirects. Preconnect to origins.

## Note

Diagnostic metric. Google suggests 800 ms as reasonable. Aim for under 200 ms for competitive performance.

## In code

<link rel="preconnect" href="https://cdn.example.com">
# Server-Timing: db;dur=53, cache;dur=22, render;dur=89

## Common questions

Q: Does a CDN always improve TTFB?

A: Yes for static cached content. For dynamic content, the CDN adds a network hop to origin.

## Thresholds

Rating: Good, TTFB Threshold: ≤ 800 ms

Rating: Needs Improvement, TTFB Threshold: 800 ms - 1.8 s

Rating: Poor, TTFB Threshold: > 1.8 s

## Key takeaways

Time until first byte of response.
Target: ≤ 800 ms (under 200 ms excellent).
Not a CWV but gates LCP and FCP.
Includes redirects, DNS, TCP/TLS, server processing.

## Related entries

Last updated July 2026. Permalink: atomicglue.co/glossary/ttfb-time-to-first-byte