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google-chromelighthouse

Lighthouse Performance values are different in report vs Profile

When running a Lighthouse (e.g. v6) via NPM package, for example:

lighthouse --view --save-assets https://example.com

Getting these numbers in the browser:

enter image description here

Then using Dev Tools > Performance > Load Profile to load the saved trace JSON, getting:

enter image description here

Question

Largest Contentful Paint 2.3s in the report vs 408.0ms in the profile. How to correlate this?

Solution

  • The Lighthouse works as expected.

    One would have to check-out the Simulated throttling:

    enter image description here

    After checked-out clicking View Trace will show the actual data in the Performance panel.

    By default Simulated throttling is checked-in, it would run the page without any throttling and then apply throttling manually to the result. In this case clicking View Trace shows the original (unthrottled) data.