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TTFB — Time to First Byte, the interval from requesting a resource until the browser receives the first response byte, including network and server processing time.
The metric represents one part of user experience, such as main-content loading, responsiveness, layout stability, or server latency. Improving one metric does not compensate for serious problems in the others.
TTFB — Time to First Byte, the interval from requesting a resource until the browser receives the first response byte, including network and server processing time.
The value is captured in a browser or lab test at a defined point in loading or interaction. Real-user field data and lab measurements can differ because of devices and networks.
First identify the resource, script, request, or layout change causing the delay. Optimize the server, critical resources, images, and JavaScript, then reassess field data.
