What does "time to first byte" measure in web performance?

"Time to first byte" (TTFB) is a crucial metric in web performance that measures the duration from the moment a client (like a web browser) sends a request to the moment the client receives the first byte of the response from the server. This takes into account several factors, including network latency, server processing time, and the time it takes to prepare the response after the request is received.

The focus on the receipt of the initial data distinguishes TTFB from other metrics. By measuring the time until the first byte is received, TTFB provides insight into how quickly a server starts responding to a user's request, which can be an indicator of server performance and responsiveness.

Understanding TTFB is essential for optimizing web applications because a high TTFB can negatively impact user experience, leading to slower page load times, which can affect engagement and conversion rates.