{"slug":"preview","title":"Preview","summary":"The preview is a web build of the same Expo project in a device frame. Pick a route or device, open the console, switch light and dark, rotate, or reload.","body":"The preview loads the current project: the real router, screens, and assets, compiled for the browser so you can click through the app without installing it.\n\n## The toolbar\n\n| Control | What it does |\n| --- | --- |\n| Route picker | Shows the current route and jumps to another one. |\n| Device picker | iPhone 15 Pro, iPad mini, or Pixel 8. |\n| Console | Log output and errors from the running app. |\n| Light / dark | Previews the app's light or dark theme. |\n| Rotate | Switches between portrait and landscape. |\n| Reload | Saves your unsaved edits, recompiles, and reloads. |\n\nYou can also open a screen from **App** on the left. Screens that need a specific record, such as a detail page, open once the app has shown that record.\n\n## While the assistant works\n\nThe assistant uses the preview to check its own screens, so the preview is locked while a turn runs. The badge shows what it is doing and on which device and route. Press **Stop** in the chat to take the preview back.\n\n## When the preview shows an error\n\nIf the project does not compile, the preview says so and points at the console. Open the console, then ask the assistant to fix the error it shows, or fix the file in **Code**. See [Troubleshooting](/docs/troubleshooting).\n\n## What the preview does not replace\n\nA browser cannot run every native module. Camera, purchases, push notifications, maps, and store signing need a device build. Use the preview for layout, copy, navigation, and flows, then check native behaviour on a phone. See [Android builds](/docs/android-builds) and [iOS builds](/docs/ios-builds).\n\n> [!NOTE]\n> The preview uses the project's single `.env`. There is no separate development environment to select.","sectionSlug":"build","sectionTitle":"Build your app","updatedAt":"2026-09-23T22:51:25.250Z","previous":{"slug":"writing-prompts","title":"Write better prompts"},"next":{"slug":"app-structure","title":"App structure"}}