Is TTFB included in LCP?

[ghisleouf]

Summary
Hi there,
Happy New Year ! (it's not yet too late !) 🎉

I'm having a question about LCP calculation.
Regarding the following diagram I got from some WebPerf experts, I'm quite perplexed about how the LCP is calculated.

As far as I can see in this diagram, TTFB is not taken into account in LCP calculation ... but, after performing several tests on Webpagetest for example, what I can see is if my TTFB is much more shorter (the test I'm running are performed on a website with very light caching), LCP is reduced drastically:

• I started with a TTFB of 4s (no cache warmup) -> LCP is 7s
• With a low TTFB (300ms) -> LCP is < 3s

So, my question is "Is TTFB taken into account is LCP duration and calculation?"

Thanks a lot for your help. 🙏

Best regards.

[adamraine]

TTFB is included in the LCP time according to Chrome's LCP definition. I believe the above diagram is misleading, where did you find it?

[ghisleouf]

Hi @adamraine ,

Thank you for your confirmation. It makes sense.
To be honest, I get this diagram from a Google WebPerf expert :)

I'm gonna update it.

Best,