What is TTFB by device pixel ratio
TTFB by device pixel ratio segments Time to First Byte (TTFB) by the screen’s pixel density. While DPR isn’t a direct cause of TTFB, it can act as a signal for the device class — and help detect performance patterns linked to device type or client hints logic.
For example, some sites adjust content or headers based on device display density — which can influence server behavior and cacheability.
Healthy TTFB by device pixel ratio sample
Should you worry
Not usually. But you should expect:
Green bars across all common DPR values
No added latency from handling device-specific content
Consistent TTFB regardless of screen density
If you’re serving the same backend response regardless of display type, this lens should be flat and clean.
Unhealthy TTFB by device pixel ratio sample
Red or yellow TTFB for a specific DPR can indicate:
Server-side logic branching based on DPR (e.g. selecting image variants or headers)
Cache misses triggered by device hints or user agent parsing
Localized content variants being dynamically selected based on screen assumptions
Heavier initial payloads or conditional HTML served to higher-end screens
Sometimes, high DPRs correlate with mobile devices on slower networks — it’s not just about the screen.
Resolving unhealthy TTFB by device pixel ratio
Go-to action plan to resolve an unhealthy TTFB by device pixel ratio:
Ask Uxi to analyze your TTFB by device pixel ratio values and suggest improvements.
Filter to correlate with different lenses and find hidden patterns.
Simulate TTFB of the suspected lens to see if fixing it will resolve the TTFB by device pixel ratio. If yes, this is where the resolution focus should be.
Use an automated optimization tool like Navigation AI to improve your TTFB by device pixel ratio values.
Once you’ve improved TTFB, set an alert to be the first to know if it starts worsening again.
Try it yourself
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