---
title: "TTFB Checker - Test Time to First Byte · Unlighthouse"
canonical_url: "https://unlighthouse.dev/tools/ttfb-checker"
last_updated: "2026-06-30T08:48:22.020Z"
meta:
  description: "Free TTFB test tool. Check your server response time with real Chrome user data (CrUX). Compare field vs lab TTFB and track trends over time."
  "og:description": "Free TTFB test tool. Check your server response time with real Chrome user data (CrUX). Compare field vs lab TTFB and track trends over time."
  "og:title": "TTFB Checker - Test Time to First Byte · Unlighthouse"
---

</h1>

```

Unlighthouse on GitHub

# **TTFB **Checker

Test Time to First Byte with real Chrome user data and lab measurements.

**Time to First Byte**Server response time

Enter a domain to check TTFB

Measures Time to First Byte (server response time)

## **Frequently Asked Questions **

<details>

<summary>**01**### **What is Time to First Byte (TTFB)?**

</summary>

Time to First Byte (TTFB) measures how long it takes for the browser to receive the first byte of response from the server after making a request. It includes DNS lookup, TCP connection, TLS handshake, and server processing time. A good TTFB is under 800ms.

</details>

<details>

<summary>**02**### **Why is TTFB important for performance?**

</summary>

TTFB directly impacts all subsequent metrics like LCP and FCP. A slow server response delays everything—the browser can't start parsing HTML, downloading resources, or rendering content until TTFB completes. Improving TTFB creates a faster foundation for your entire page load.

</details>

<details>

<summary>**03**### **What causes slow TTFB?**

</summary>

Slow TTFB is typically caused by: slow server-side processing, database query delays, no server-side caching, distance between user and server (no CDN), unoptimized backend code, shared hosting resource limits, and cold starts on serverless functions.

</details>

<details>

<summary>**04**### **How do I improve my TTFB?**

</summary>

To improve TTFB: use a CDN to serve content closer to users, implement server-side caching (Redis, Varnish), optimize database queries, use edge rendering or SSR at the edge, upgrade hosting infrastructure, enable HTTP/2 or HTTP/3, and reduce server-side processing complexity.

</details>

<details>

<summary>**05**### **What is the difference between origin and URL TTFB in CrUX?**

</summary>

Origin TTFB is the aggregate across all pages on your domain from real Chrome users. URL TTFB is specific to a single page. Origin data has more samples and is more stable, while URL data shows page-specific performance but may have insufficient data for low-traffic pages.

</details>

### **Learn More About Web Performance **

[**LCP Guide **](https://unlighthouse.dev/learn-lighthouse/lcp) [** Core Web Vitals **](https://unlighthouse.dev/learn-lighthouse/core-web-vitals) [** TTFB Glossary **](https://unlighthouse.dev/glossary/ttfb)