What is TTFB by FCP
TTFB by FCP shows how Time to First Byte (TTFB) - the server response speed, relates to First Contentful Paint (FCP) - when the first content appears.
While TTFB and FCP are both early-phase metrics, they represent different layers: TTFB is server-side, FCP is browser-side. This lens helps you connect backend performance with early visual rendering — and see how backend delays cascade into slow perceived loads.
Healthy TTFB by FCP sample
Should you worry
A healthy TTFB by FCP lens shows:
Fast TTFB sessions usually have fast FCP.
Backend response times are short, enabling early HTML and CSS rendering.
Users see something quickly and gain confidence that the page is loading.
This is ideal: the server responds fast, and the browser renders just as quickly.
Unhealthy TTFB by FCP sample
Unhealthy patterns include:
Slow TTFB, slow FCP: Server takes too long, so the browser has nothing to render. Classic sign of a cold backend, heavy CMS, or poor edge caching.
Fast TTFB, slow FCP: Server is quick, but frontend rendering is slow. Could point to inefficient critical CSS, blocking JS, or render pipeline issues.
Slow TTFB, fast FCP: Rare and usually not sustainable — may indicate edge optimizations like partial hydration masking deeper issues.
This lens shows whether the server is dragging down the visual start of the experience.
Resolving unhealthy TTFB by FCP
Go-to action plan to resolve an unhealthy TTFB by FCP:
Ask Uxi to analyze your TTFB by FCP values and suggest improvements.
Use Filters to drill into specific routes or traffic sources affected by poor FCP.
Simulate TTFB of the suspected lens to see if fixing it will resolve the TTFB by FCP. If yes, this is where the resolution focus should be.
Use an automated optimization tool like Navigation AI to improve your TTFB by FCP values.
Once you’ve improved TTFB, set an alert to be the first to know if it starts worsening again.
Try it yourself
Discover how your website performs with real user data.