FCP is shorter than reported Server Response Time

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I Biron Ren

Oct 29, 2021, 3:41:00 PM10/29/21
to Chrome UX Report (Discussions)

I was testing pagespeed on the site in the screenshot below and encountered something I'd never seen before - the FCP time was shorter than the Server Response Time reported in PSI. I'm looking for some clarification on how this happens/how exactly FCP is calculated. 

My understanding is that FCP includes the TTFB, and LCP includes FCP as well as TTFB. So, each metric measuring starting at the time the initial request is sent out by the browser. Is this not the case? 

Screen Shot 2021-10-29 at 3.30.28 PM.png

Rick Viscomi

Nov 1, 2021, 1:16:15 PM11/1/21
to I Biron Ren, Chrome UX Report (Discussions)
I agree something doesn't look right. Could you file an issue in the Lighthouse GitHub repo?

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I Biron Ren

Nov 1, 2021, 1:36:25 PM11/1/21
to Chrome UX Report (Discussions), rvis...@google.com, Chrome UX Report (Discussions), I Biron Ren
Not sure if I filled the issue report out properly but I've submitted it there. Thanks! 
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