Time to First Byte (TTFB)

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Time to First Byte (TTFB) measures how quickly a server starts responding to a request. It includes DNS lookup, connection time, TLS negotiation, and server processing before the first byte of content is returned. A high TTFB delays everything downstream, including rendering and interactivity.

What TTFB Includes

Redirect time (if any)
DNS resolution
TCP connection and TLS handshake
Server request handling
Time until the first response byte arrives

TTFB is not the full page load time, but it is a critical early signal of backend and network health.

Why TTFB Matters

Faster Starts Compound

Every later performance metric waits on the first byte. Slow TTFB pushes out LCP and overall load.

Backend Visibility

TTFB helps distinguish server/application delays from front-end rendering issues.

SEO and UX Impact

Poor server responsiveness contributes to weak page experience, especially on content-heavy or dynamic sites.

Common Causes of High TTFB

Slow server-side rendering or database queries
Cold starts in serverless environments
Inefficient application logic or uncached APIs
Distant origin servers without edge caching
Overloaded hosting infrastructure
Expensive middleware or authentication checks

How to Improve TTFB

Cache HTML or API responses where possible
Use a CDN and edge caching for static or semi-static content
Optimize database queries and backend code paths
Enable HTTP/2 or HTTP/3 and keep connections efficient
Reduce origin work with precomputing or incremental rendering
Choose hosting regions close to your users
Monitor real-user TTFB by geography and route

Measuring TTFB

TTFB can be measured with:

Browser DevTools Network panel
Web Vitals and RUM tooling
Lighthouse and lab testing tools
Server logs and APM platforms

Always compare lab and field data. Local tests can hide regional latency and production cache behavior.

Practical Benchmarks

There is no single universal target, but many teams aim for a TTFB well under a few hundred milliseconds for cached or simple responses. Dynamic personalized pages may be higher, but should still be actively optimized.

Improving TTFB is often about removing unnecessary server work and moving responses closer to users.