Performance Lab · LAB-05Under investigation
“100 Lighthouse means your website is perfect.”
Lighthouse is a synthetic run on a simulated device, on your network, with no real user in sight. It is a useful ratchet, not a verdict.
- Verdict
- BUSTED
- Level
- DEVELOPER
- Division
- LAB-05
- References
- 02
Investigation
Lighthouse measures a single cold load under simulated throttling. Real users arrive with warm caches and cold ones, on flaky networks, on devices five years older than yours, from further away, with extensions installed, and they interact, which is where INP lives and where synthetic runs have the least to say.
| Lab (Lighthouse) | Field (CrUX / RUM) | |
|---|---|---|
| Question answered | Did my change help? | What did users experience? |
| Variance | Low, reproducible | High, real |
| Interaction coverage | Minimal | Complete |
| Device profile | One simulated device | Everything your users own |
References
- 01ChromeLighthouse documentation
- 02web.devLab and field data