INP degradation on mobile since March '25

[Adam Cable]

Hi,

We have noticed a considerable degradation of our INP scores on mobile from the beginning of March, but strangely haven't made any code changes at all around this time.

Do you know if there's been any changes in the way the INP metric has been calculated around this time? Any insights would be very useful - thanks :)

Adam

[Barry Pollard]

Not aware of any big changes, and there's nothing in the INP changelog.

Additionally, we're not seeing a system-wide INP regression.

Do you have a site you can share (even if privately)?

[Adam Cable]

Will pop you a note - thank you :)

Adam

[Francesc Invernon]

Hi,

We've seen the same from 28 february, nothing changed on our side, but a drop in good INP URLS ins GoogleSearchConsole, and a increase of need to improve ones. 

[Teo Turner]

Hi,

Adding to the tally of experiencing an unexplained INP increase around the same date with no code changes.

More importantly I'm able to see the same INP issues on websites across the web.

Here's a public example.

https://csszengarden.com/

Very simple site but when you set the size to a mobile device on Chrome INP jumps to ~150-200ms INP even when clicking on <p> tags, no issues on desktop.
I can't see any good reason for it, I suspect something has changed browser side.

It's also not a measurement issue as the delay is perceivable on interactions that update page styles.

[Barry Pollard]

I think this is an instance of this bug:
https://issues.chromium.org/issues/409577163

Does this only happen in Chrome Dev Tools when in mobile emulation? And only for the first tap? And does it not happen when debugging on a real device?

If so, the good news is this doesn't appear to affect real users (as shown by your excellent INP score). But I appreciate it's annoying when debugging INP. I will see if I can raise the priority of this with the DevTools team.

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