Desktop and mobile
Toggle the device before running the test to measure with Lighthouse's desktop or mobile profile — the throttling and viewport differ, and mobile scores are usually lower, so test the one that matches your audience.
See what's slowing the page down
Beyond the scores, the report lists the biggest performance opportunities — render-blocking resources, oversized images, inefficient caching — each with an explanation so you know what to fix.
Frequently asked
- Is this lab or field data?
- It's lab data from a Lighthouse run in a controlled headless browser — great for debugging and before/after comparisons.
- What's a good LCP?
- Google considers LCP under 2.5s 'good', 2.5–4s 'needs improvement', and over 4s 'poor'.