TTFB

Time to First Byte (TTFB) is a foundational performance metric. It measures the time between the browser's request for a page and the arrival of the first byte of data from the server. While metrics like LCP focus on the front-end, TTFB is the primary indicator of server responsiveness and network efficiency.

How TTFB is calculated

TTFB isn't a single measure — it's the result of three distinct phases working together:

• Request transmission — How fast the browser's request reaches the server over the network.
• Server processing — How long the server spends handling the request: executing application logic (PHP, Node.js), querying databases, and generating the HTML.
• Response delivery — How quickly the first byte of the generated response is sent back to the user's browser.

Target benchmarks

Several tools are available for measuring TTFB. We recommend FlyingTTFB↗ for unlimited global results.

The table below outlines the recommended performance ranges and how each impacts user experience:

TTFB range	Rating	Notes
< 200 ms	Gold standard	High-performance sites.
< 600 ms	Good	Acceptable performance for most sites.
600 – 1,800 ms	Needs improvement	Will impact user experience.
> 1,800 ms	Poor	Likely to cause noticeable delays.