Lighthouse and PageSpeed Insights are page audits run on a simulated device in Google's infrastructure. That is useful and free — but the phone it emulates is not the phone your customer owns. Redline measures the machine in front of you and tells you where its ceiling is.
| Dimension | Lighthouse / PSI | Redline |
|---|---|---|
| Device model | A simulated mid-tier phone with throttled CPU | The actual hardware running the test |
| Hardware signal | None — the machine is emulated | Cores, memory, GPU renderer, DPR, connection |
| Score meaning | How this page performs in a lab | How much headroom this device has, on any page |
| Cohort context | None | Percentile against every device tested |
| Diagnosis | Rule-based audit list | AI reading of the device profile plus the metrics |
| Best used for | Page-level regressions in CI | Deciding which devices you can still support |
Keep Lighthouse for page regressions. Use Redline when the question is "which devices are we losing?" — then set a device-score floor and gate releases on it with the Redline CI endpoint.
Test your device