What Is Time to First Byte and Why It Matters
Learn what TTFB measures, what causes it to rise, and how it affects perceived frontend speed.
What Is Time to First Byte and Why It Matters
Time to first byte, or TTFB, measures how long it takes from the initial request until the browser receives the first byte of the response. It is a useful proxy for backend and network responsiveness.
What TTFB Includes
TTFB covers DNS lookup, connection setup, TLS negotiation, request processing, and the time until the first response byte arrives.
Why It Matters
High TTFB makes pages feel slow before rendering even starts. Users experience the delay as a blank or frozen interface.
Common Causes
- Slow server processing
- Cold starts
- Slow database queries
- Network latency
- Poor caching
How Frontend Engineers Use It
Frontend engineers use TTFB to separate server delay from client rendering delay. If TTFB is high, the problem is often before the browser receives meaningful data.
The Takeaway
TTFB is not the whole performance story, but it is a critical early metric. Improving it makes the rest of the frontend pipeline start sooner.
TTFB is the time from the request being sent until the browser receives the first byte of the response.
No. It mainly reflects network and server processing time before the browser starts receiving the response body.
Because the browser cannot start rendering useful content until it receives the response, so the page feels blank or stuck.
Slow server processing, cold starts, slow databases, network latency, and weak caching are common causes.
Use CDNs, caching, smaller responses, and ensure the backend responds quickly for the critical path.
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