Suggest an editImprove this articleRefine the answer for “What does the Performance tab do?”. Your changes go to moderation before they’re published.Approval requiredContentWhat you’re changing🇺🇸EN🇺🇦UAPreviewTitle (EN)Short answer (EN)**The Performance tab** in Chrome DevTools records and shows what happens in the browser at the engine level while a page loads and runs. **Key point:** the Performance tab is like an X-ray for the browser: it shows exactly how the site lives inside and where it loses speed.Shown above the full answer for quick recall.Answer (EN)ImageThe **Performance** tab in Chrome DevTools records and shows what happens in the browser at the engine level while a page loads and runs. --- ### What it does: 1. **Records a timeline of page activity** - parsing, rendering, JS execution, network requests, GC, events, and so on - lets you see when and why slowdowns happen 2. **Shows JavaScript loading and execution** - which scripts ran, how long they took, whether they blocked the main thread 3. **Profiles rendering** - Layout, Paint, Composite, which elements triggered recalculations or repaints 4. **Reveals blocking** - long tasks (> 50 ms), main thread blocking - helps you understand where and why the interface "did not respond" 5. **Shows key Web Vitals (LCP, FCP, TTI)** - you can find them right on the timeline --- ### How to use it: 1. Open the **Performance** tab 2. Click the ● Record button 3. Reload the page or perform actions 4. Click ■ Stop 5. Study the timeline: - frames (FPS) at the top - below: script execution time, rendering, layout, paint - click on sections to see details (exactly what ran and why) --- ### What it gives you: - an exact understanding of where the site slows down - which tasks block the thread - which events trigger unnecessary layout/paint - helps optimize load time and responsiveness --- **Conclusion:** The Performance tab is like an X-ray for the browser: it shows exactly how your site lives inside and where it loses speed.For the reviewerNote to the moderator (optional)Visible only to the moderator. Helps review go faster.