Webpagetest's Lighthouse: field or lab?

Question

Webpagetest.org offers "own" Lighthouse test. It can run as a part of the general WPT test or as a standalone test from the URL /lighthouse.

My question: is the WPT's Lighthouse test a LAB or a FIELD ?

I've got this question because of the following experience:

I've fixed a CLS issue on a website. I realized the CLS issue was gone when I tested this website with Lighthouse out of Chrome DevTools and PageSpeed Insights.

In the PageSpeed Insights results, it was displayed very clear:

• while the field data displayed the CLS issue (correct, because this is the data from the past 28 days, and I fixed the issue just today),
• the lab data displayed no CLS issue (correct too - the lab data comes in real-time from a specific environment).

And then, I tested the website with WPT's Lighthouse the CLS issue was displayed again. This is the cause, why I think WPT's Lighthouse data is the field and decided to ask.

PS: Firstly I thought to publish this question at https://webmasters.stackexchange.com/, but the most important tag [webpagetest] doesn't exist there.

Answer 1

It was my fail on terminology.

Lighthouse does always lab tests, independently of where it starts. On PageSpeed Insights there are just two different results sources:

1. Field data, from CrUX database,
2. Lab data, from Lighthouse test