timetofirstbyte

Time to First Byte (TTFB) is a web performance metric that measures the time elapsed from when a client makes an HTTP request to when the first byte of the response is received. In practice, the exact start and end points can vary, but TTFB is commonly defined as the interval from request initiation to the arrival of the first response byte. This interval encompasses several potential sub-lages: DNS lookup, establishing a TCP connection, any TLS handshake, and the server’s processing time before it begins transmitting data.

TTFB is influenced by both network factors and server-side processing. Network latency, congestion, and geographical distance between client and server can increase TTFB, while server-side queuing, application logic, database calls, and backend services can also add delays. Caching and content delivery networks (CDNs) can markedly reduce TTFB by serving cached responses closer to the user or by reducing server processing.

Common tools to measure TTFB include browser developer tools (the Network panel), Lighthouse, WebPageTest, and various command-line utilities such as curl with a head request. Interpreting TTFB requires context: very low values are desirable, but a low TTFB does not guarantee fast page rendering if the total payload is large or the front-end work is heavy.

Optimization strategies include reducing server processing time, optimizing database queries, enabling caching at the edge or page level, using a CDN, enabling keep-alive, minimizing redirects, and adopting modern transport protocols (HTTP/2 or HTTP/3) to improve connection efficiency.