Page speed
Time to First Byte
TTFB under 800 ms; critical over 1.8 s
What we check
TTFB under 800 ms; critical over 1.8 s
Why it matters
Every later milestone waits on the first byte.
How to fix it
Add caching or a CDN, and speed up the server response.
How it affects your score
This check sits in Page speed, which is worth 20% of the overall score. A critical result costs the full weight of the check; a warning costs half. If we can't measure it on your page, we leave it out of the score entirely.