SERP Lens measures Core Web Vitals using the PageSpeed Insights API, giving you performance data for any page. These metrics are ranking signals in Google Search and directly affect user experience.
The three metrics
Largest Contentful Paint (LCP)
Measures how long it takes for the largest visible element (image, video, or text block) to render.
| Rating | Threshold |
|---|
| Good | ≤ 2.5 seconds |
| Needs improvement | 2.5–4.0 seconds |
| Poor | > 4.0 seconds |
Interaction to Next Paint (INP)
Measures responsiveness — how quickly the page responds to user interactions (clicks, taps, key presses).
| Rating | Threshold |
|---|
| Good | ≤ 200 milliseconds |
| Needs improvement | 200–500 milliseconds |
| Poor | > 500 milliseconds |
Cumulative Layout Shift (CLS)
Measures visual stability — how much the page layout shifts unexpectedly during loading.
| Rating | Threshold |
|---|
| Good | ≤ 0.1 |
| Needs improvement | 0.1–0.25 |
| Poor | > 0.25 |
Because data comes from the PageSpeed Insights API, there may be a short delay before results appear. Browser settings like network throttling, device emulation, and VPN do not affect these results — the API runs its own independent test. Local browser-based measurements are planned for the future.
Next steps
