How it works

Real‑user monitoring vs. lab tests

Lab tools (e.g., synthetic Lighthouse runs) estimate performance on controlled hardware and networks. Useful for debugging, but they don’t necessarily reflect how your users experience your site.

Speed Insights uses RUM—metrics measured directly in real browsers. This shows the experience your users actually have, accounting for their network, device, and content.

What is a data point?

A data point is a single measurement reported from a browser for one metric on one page load (e.g., a single LCP value for /pricing). Dashboard “Data points” show how many raw measurements a percentile/score is based on.

Percentiles

Percentiles summarize distributions:

• P50: Median (typical user).
• P75: The fastest 75% of experiences (commonly used for Core Web Vitals).
• P90: Includes more of the long tail; good for spotting edge‑case slowness.

The dashboard defaults to p75. You can switch to p50 or p90 when supported in the view you’re using.

Device types

Metrics are split by device type:

• Desktop
• Mobile

This helps you compare experiences and prioritize fixes for the right platform.