Suggest an editImprove this articleRefine the answer for “What does zone.js do when the application starts?”. Your changes go to moderation before they’re published.Approval requiredContentWhat you’re changing🇺🇸EN🇺🇦UAPreviewTitle (EN)Short answer (EN)In Angular, `zone.js` is a library that **tracks asynchronous operations in the application** and helps Angular automatically run **change detection** after they complete. **Key point:** `zone.js` provides automatic change detection after asynchronous operations, which lets the interface always stay up to date without manual intervention.Shown above the full answer for quick recall.Answer (EN)ImageIn Angular, `zone.js` is a library that **tracks asynchronous operations in the application** and helps Angular automatically run **change detection** after they complete. ## Key points 1. **Intercepting asynchronous events** - `zone.js` "wraps" timers (`setTimeout`, `setInterval`), promises, HTTP requests, and DOM events. - When such operations complete, Angular knows it needs to update the interface. 2. **Automatically running change detection** - After every asynchronous event, Angular automatically checks the components and updates the DOM. - This frees the developer from having to call `detectChanges()` manually. 3. **When the application starts** - `zone.js` is picked up in `main.ts` through the `import 'zone.js'` import. - All the application's asynchronous tasks fall inside the "zone," and Angular tracks their completion. In other words, `zone.js` **provides automatic change detection after asynchronous operations**, which lets the interface always stay up to date without manual intervention.For the reviewerNote to the moderator (optional)Visible only to the moderator. Helps review go faster.