Lighthouse Test Missing Throttling

Hi All,

I completed two Webpagetests:

  • One on May 8th
  • On Today 29th July

Looking at the lighthouse results, I can see that network throttling was only applied to one lighthouse test, which I fear is affecting the post-implementation results as I have some metrics increase odly.

I have attached screenshots for both test settings, would be great to understand more how this could happen!



The reported throttling settings inside of the Lighthouse report don’t show the whole picture.

On the May 8th test the Network throttling was applied outside of lighthouse at the packet layer using NetEm and Lighthouse was configured to do the CPU throttling.

Today’s test ran Lighthouse in “Simulate” mode which is the default mode Lighthouse uses but is less accurate. It doesn’t apply any actual throttling directly but it models what the performance would have been like if it had throttled.

The change is because of this issue with Lighthouse that we are working through sorting out with the Lighthouse team. Lighthouse is failing in a lot of tests with Chrome 92 when using the real throttling so we switched WPT until it can get sorted out.

A few minutes ago I added another checkbox to the “Chrome” tab below the lighthouse checkbox that lets you opt to use the real emulation but there’s a good chance you will get a failed Lighthouse test if you enable it.

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Hi @pmeenan ,

Thank you very much, this is really helpful!