How to Read Performance Reports

Learn how to interpret performance metrics and understand what impacts user experience and SEO.

Performance Report Overview

Performance reports provide a detailed breakdown of how fast, responsive, and stable your page is under real-world conditions. These metrics help identify bottlenecks and prioritize optimizations.

The Performance Score

At the top of each report, you’ll see a performance score ranging from 0 to 100. This score summarizes overall page performance.

  • 90–100 (Green): Excellent — the page is well optimized.
  • 50–89 (Orange): Needs improvement.
  • 0–49 (Red): Poor — immediate attention recommended.

The score is influenced by multiple performance metrics, weighted by their impact on user experience.

Core Web Vitals

Core Web Vitals are Google’s primary metrics for measuring real user experience.

  • LCP (Largest Contentful Paint): Measures loading performance by tracking how long it takes for the largest visible element to render.
    Target: < 2.5 seconds
  • CLS (Cumulative Layout Shift): Measures visual stability by tracking unexpected layout shifts.
    Target: < 0.1
  • INP (Interaction to Next Paint): Measures responsiveness by tracking the delay between user interaction and visual feedback.
    Target: < 200 ms

Additional Performance Metrics

  • FCP (First Contentful Paint): Time taken for the first piece of content (text or image) to appear.
  • TTFB (Time to First Byte): Time taken for the server to respond to the initial request. High values may indicate backend or hosting issues.
  • Speed Index: Measures how quickly the page contents are visually displayed.
  • Total Blocking Time (TBT): Amount of time the main thread is blocked by long JavaScript tasks, preventing user interaction.
  • DOM Content Loaded: Time when the HTML document has been fully loaded and parsed.
  • Fully Loaded Time: Time taken for all page resources to finish loading.

Opportunities & Diagnostics

Below the metrics, performance reports include automatically generated insights to help you improve your scores.

  • Opportunities: Actionable recommendations that can directly improve performance, such as optimizing images or reducing unused JavaScript.
  • Diagnostics: Additional technical details that help identify inefficiencies and root causes.

Desktop vs Mobile Reports

Performance reports are generated separately for desktop and mobile devices.

Mobile reports typically show lower scores due to slower network speeds and reduced device performance. Always prioritize mobile optimization, as it has a greater impact on user experience and SEO.

Using Reports to Improve Performance

Use performance reports to identify trends, track improvements over time, and validate changes after deployments.

Re-running analyses after fixes helps confirm that optimizations have had the desired impact.