[Question] Why is FCP not an attribution for LCP? about web-vitals HOT 4 CLOSED

So why is FCP not packaged as an LCP attribution? It seems very useful and relevant.

The reason is because the current LCP breakdown metrics actually provide more information than FCP provides, so it makes more sense to use them.

FCP is a useful metric if you want to optimize for a fast first paint, but if you are only wanting to Optimize LCP then FCP may or may not be helpful as an attribution signal. For example, if you have a page with a render-blocking stylesheet, that will likely delay FCP but (depending on the size of the stylesheet) it may or may not have any impact on LCP.

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Thanks! FCP is not always relevant to LCP, so it's not an LCP attribution.

FCP is a useful metric if you want to optimize for a fast first paint

Should FP also be an attribution for FCP then?

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Should FP also be an attribution for FCP then?

The vast majority of the time, FP and FCP end up being the exact same time, so in general FP is not useful as a diagnostic metric for FCP.

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Sounds good. Thanks

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