What it means in plain language
TTFB, i.e. Time to First Byte, is the time from sending the request to receiving the first byte of the response from the server.
Where it genuinely helps
TTFB measures time to the first response byte and can reveal server, network or cache delay without describing complete rendering.
What to decide before acting
Measure HTML and APIs separately from several locations, with warm and cold cache, before assigning one cause.
How to tell whether it works
Compare medians and high percentiles with backend logs, DNS, TLS, CDN and real-user Core Web Vitals.
