CrUX and DevTools

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Szczepan Bielecki (Pimko)

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Aug 22, 2025, 8:06:58 AM Aug 22

to Chrome UX Report (Discussions)

Hello,

I wonder if every page load with open DevTools sends CWV data to the CrUX dataset?

Does setting disable cache or simulating e.g. 4x slowdown devices also count, and does data send?

Regards,

Szczepan

Barry Pollard

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Aug 22, 2025, 8:12:35 AM Aug 22

to Szczepan Bielecki (Pimko), Chrome UX Report (Discussions)

I wonder if every page load with open DevTools sends CWV data to the CrUX dataset?

Having DevTools open or closed doesn't change whether a page's experience data is sent to CrUX. Those page loads follow the usual criteria just like any other page load.

Does setting disable cache or simulating e.g. 4x slowdown devices also count, and does data send?

Yes we measure the end user experience. So if that is slowed down, and you meet the criteria for sending data, then yes those slow page loads will be included in CrUX.

In most cases, for sites popular enough to appear in CrUX hopefully the developers are but a very small sample of the overall page loads and not having a statistically significant impact on the overall CrUX numbers. Having DevTools open is often useful to debug what exactly is being sent to CrUX ( good guide on that here ) so devs using that wouldn't want DevTools being open to exclude this.

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