Why does pagespeed throw different performance scores on different browsers?

Question

I'm testing my site on PSI and see varying results on Edge vs Chrome (both are on incognito).

This difference could be based on other factors - which I haven't been able to determine. But for now, it seems to be different based on which browser I test this in.

That doesn't make sense to me, as the browser should not affect PSI scores.

Browser: "Edge"
Performance score: 37
CLS: 0.121

Browser: "Chrome"
Performance score: 65
CLS: 0.061

Philip Walton · Answer

The browser you're running does not affect PSI scores (the tests are run on a server, not on your machine), but PSI scores can vary from run to run, see this doc for a list of reasons why: https://github.com/GoogleChrome/lighthouse/blob/master/docs/variability.md

Why does pagespeed throw different performance scores on different browsers?

1 Answers