---
title: "What is Time to First Byte (TTFB)? · Unlighthouse"
meta:
  "og:description": "TTFB measures server response time. Learn what it is, thresholds, and how to optimize it."
  "og:title": "What is Time to First Byte (TTFB)? · Unlighthouse"
  description: "TTFB measures server response time. Learn what it is, thresholds, and how to optimize it."
---

**Glossary**

# **What is Time to First Byte (TTFB)?**

[Copy for LLMs](https://unlighthouse.dev/glossary/ttfb.md)

Time to First Byte (TTFB) measures how long until the browser receives the first byte from the server. It's a foundational metric - nothing can render until this completes.

## [Thresholds](#thresholds)

| **Score** | **Rating** |
| --- | --- |
| ≤ 800ms | Good |
| 800ms - 1800ms | Needs Improvement |
| > 1800ms | Poor |

[**Google recommends**](https://web.dev/articles/ttfb) 800 milliseconds or less.

## [What TTFB Includes](#what-ttfb-includes)

- Redirect time
- DNS lookup
- TCP connection
- TLS negotiation
- Server processing time

Sites with poor [**LCP**](https://unlighthouse.dev/glossary/lcp) have an [**average TTFB of 2,270ms**](https://almanac.httparchive.org/en/2024/performance) - nearly consuming the entire 2.5s LCP budget.

## [Why It Matters](#why-it-matters)

TTFB is the starting point for all other metrics. High TTFB delays [**FCP**](https://unlighthouse.dev/glossary/fcp), [**LCP**](https://unlighthouse.dev/glossary/lcp), and everything else. For SPAs, fast TTFB is especially critical since client-side rendering adds more time.

## [Common Issues](#common-issues)

- Slow server processing / database queries
- No caching (regenerating cacheable responses)
- Geographic distance without CDN
- Too many redirects

## [Improve TTFB](#improve-ttfb)

- Use a CDN
- Enable caching at all levels
- Optimize backend code
- Use HTTP/2 or HTTP/3
- Minimize redirects

## [Measure TTFB](#measure-ttfb)

- Chrome DevTools Network panel ("Waiting for server response")
- [**PageSpeed Insights**](https://pagespeed.web.dev/)
- WebPageTest waterfall

TTFB is not a Core Web Vital, but directly impacts [**LCP**](https://unlighthouse.dev/glossary/lcp) which is. Slow TTFB makes good LCP nearly impossible.

[Edit this page](https://github.com/harlan-zw/unlighthouse/edit/main/docs/glossary/ttfb.md)

[Markdown For LLMs](https://unlighthouse.dev/glossary/ttfb.md)

**Did this page help you? **

Anything that could be done better? :)

Help us improve this page. You can [edit this page](https://github.com/harlan-zw/unlighthouse/edit/main/docs/glossary/ttfb.md) on GitHub or provide anonymous feedback below.

[**TBT** TBT measures main thread blocking during load. Learn what it is, thresholds, and how to reduce blocking time.](https://unlighthouse.dev/glossary/tbt) [**TTI (Deprecated)** TTI measured page interactivity but was deprecated in Lighthouse 10. Learn what replaced it.](https://unlighthouse.dev/glossary/tti)

**On this page **

- [Thresholds](#thresholds)
- [What TTFB Includes](#what-ttfb-includes)
- [Why It Matters](#why-it-matters)
- [Common Issues](#common-issues)
- [Improve TTFB](#improve-ttfb)
- [Measure TTFB](#measure-ttfb)