What is TTFB by device CPU cores
TTFB by device CPU cores shows the Time to First Byte (TTFB) across devices with varying CPU core counts (e.g. 2, 4, 8 cores). This lens helps you identify whether backend responsiveness is being affected by the user's device processing power.
Only devices with relevant CPU configurations that reached your site during the selected period will be listed.
Unlike INP or LCP, TTFB isn’t usually affected by hardware — but on very low-core devices with poor networking stacks or aggressive CPU throttling (e.g. on mobile), it can show degradation.
Healthy TTFB by device CPU cores sample
Should you worry
A healthy TTFB by device CPU cores lens shows all green. That means no noticeable delay in server responses across devices, regardless of their core count.
Unhealthy TTFB by device CPU cores sample
In the example below, users on 4-core devices experience slower TTFB. These delays can impact the perceived performance of your site, especially on mobile.
Resolving unhealthy TTFB by device CPU cores
Go-to action plan to resolve an unhealthy TTFB by device CPU cores:
Ask Uxi to analyze your TTFB by device CPU cores values and suggest improvements.
Use Filters these devices and examine their geographic location, connection type, or service worker status to determine if there's correlation.
Simulate TTFB of the suspected lens to see if fixing it will resolve the TTFB by device CPU cores. If yes, this is where the resolution focus should be.
Use an automated optimization tool like Navigation AI to improve your TTFB by device CPU cores 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.