Lighthouse and Core Web Vitals answer different questions. Lighthouse runs a controlled lab test now; Core Web Vitals summarize how real Chrome users experienced a page over time.
Use Lighthouse to diagnose
A Lighthouse report helps reproduce loading problems, compare code changes and find technical opportunities. It can measure LCP and CLS in the lab, but it cannot directly measure field INP because there is no real user interacting with the simulated load. TBT is the useful lab diagnostic for main-thread blocking.
Use field data to understand visitors
Real-user Core Web Vitals are LCP, INP and CLS. They are aggregated across visits and are best for understanding the experience people actually received. A page can have a weak lab score and still pass field data, or the reverse.
The practical workflow
- Use field data to identify pages and metrics that affect real users.
- Use a fresh Lighthouse test to reproduce likely causes.
- Make one controlled improvement.
- Retest in the lab, then watch field data over time.