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<!DOCTYPE html><html><head><meta charset="utf-8"><meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1"><title>Debugging React Native | A framework for building native apps using React</title><meta name="viewport" content="width=device-width"><meta property="og:title" content="Debugging React Native | A framework for building native apps using React"><meta property="og:type" content="website"><meta property="og:url" content="http://facebook.github.io/react-native/index.html"><meta property="og:image" content="http://facebook.github.io/react-native/img/opengraph.png?2"><meta property="og:description" content="A framework for building native apps using React"><base href="/react-native/releases/next/"><link rel="stylesheet" href="https://cdn.jsdelivr.net/docsearch.js/1/docsearch.min.css"><link rel="shortcut icon" href="img/favicon.png?2"><link rel="stylesheet" href="css/react-native.css"><script type="text/javascript" src="//use.typekit.net/vqa1hcx.js"></script><script type="text/javascript">try{Typekit.load();}catch(e){}</script></head><body><div class="container"><div class="nav-main"><div class="wrap"><a class="nav-home" href=""><img src="img/header_logo.png">React Native</a><a class="nav-version" href="/react-native/versions.html">next</a><div class="nav-site-wrapper"><ul class="nav-site nav-site-internal"><li><a href="docs/getting-started.html" class="active" data-target=".nav-docs">Docs</a></li><li><a href="support.html" class="">Support</a></li><li><a href="showcase.html" class="">Showcase</a></li><li><a href="blog/" class="">Blog</a></li></ul><div class="algolia-search-wrapper"><input id="algolia-doc-search" type="text" placeholder="Search docs..."></div><ul class="nav-site nav-site-external"><li><a href="https://github.com/facebook/react-native" class="">GitHub</a></li><li><a href="http://facebook.github.io/react" class="">React</a></li></ul></div></div></div><section class="content wrap documentationContent"><div class="nav-docs"><div class="nav-docs-viewport"><div class="nav-docs-section"><h3>Quick Start</h3><ul><li><a style="margin-left:0;" class="" href="docs/getting-started.html">Getting Started</a></li></ul></div><div class="nav-docs-section"><h3>Tutorials</h3><ul><li><a style="margin-left:0;" class="" href="docs/tutorial-core-components.html">Core Components</a></li><li><a style="margin-left:0;" class="" href="docs/tutorial-integration-with-existing-apps.html">Integration With Existing Apps</a></li></ul></div><div class="nav-docs-section"><h3>Sample Applications</h3><ul><li><a style="margin-left:0;" class="" href="docs/sample-application-movies.html">Movie Fetcher</a></li><li><a target="_blank" style="margin-left:0;" class="" href="http://makeitopen.com/">F8 2016 App</a></li></ul></div><div class="nav-docs-section"><h3>Community Resources</h3><ul><li><a style="margin-left:0;" class="" href="docs/videos.html">Videos</a></li><li><a target="_blank" style="margin-left:0;" class="" href="http://reactnative.cc/">Newsletter</a></li></ul></div><div class="nav-docs-section"><h3>Guides</h3><ul><li><a style="margin-left:0;" class="" href="docs/style.html">Style</a></li><li><a style="margin-left:0;" class="" href="docs/images.html">Images</a></li><li><a style="margin-left:0;" class="" href="docs/gesture-responder-system.html">Gesture Responder System</a></li><li><a style="margin-left:0;" class="" href="docs/animations.html">Animations</a></li><li><a style="margin-left:0;" class="" href="docs/accessibility.html">Accessibility</a></li><li><a style="margin-left:0;" class="" href="docs/direct-manipulation.html">Direct Manipulation</a></li><li><a style="margin-left:0;" class="active" href="docs/debugging.html">Debugging</a></li><li><a style="margin-left:0;" class="" href="docs/testing.html">Testing</a></li><li><a style="margin-left:0;" class="" href="docs/javascript-environment.html">JavaScript Environment</a></li><li><a style="margin-left:0;" class="" href="docs/navigator-comparison.html">Navigator Comparison</a></li><li><a style="margin-left:0;" class="" href="docs/known-issues.html">Known Issues</a></li><li><a style="margin-left:0;" class="" href="docs/performance.html">Performance</a></li><li><a style="margin-left:0;" class="" href="docs/upgrading.html">Upgrading</a></li><li><a style="margin-left:0;" class="" href="docs/platform-specific-code.html">Platform Specific Code</a></li></ul></div><div class="nav-docs-section"><h3>Guides (iOS)</h3><ul><li><a style="margin-left:0;" class="" href="docs/native-modules-ios.html">Native Modules</a></li><li><a style="margin-left:0;" class="" href="docs/native-components-ios.html">Native UI Components</a></li><li><a style="margin-left:0;" class="" href="docs/linking-libraries-ios.html">Linking Libraries</a></li><li><a style="margin-left:0;" class="" href="docs/running-on-device-ios.html">Running On Device</a></li><li><a style="margin-left:0;" class="" href="docs/communication-ios.html">Communication between native and React Native</a></li></ul></div><div class="nav-docs-section"><h3>Guides (Android)</h3><ul><li><a style="margin-left:0;" class="" href="docs/native-modules-android.html">Native Modules</a></li><li><a style="margin-left:0;" class="" href="docs/native-components-android.html">Native UI Components</a></li><li><a style="margin-left:0;" class="" href="docs/running-on-device-android.html">Running On Device</a></li><li><a style="margin-left:0;" class="" href="docs/signed-apk-android.html">Generating Signed APK</a></li><li><a style="margin-left:0;" class="" href="docs/android-ui-performance.html">Profiling Android UI Performance</a></li><li><a style="margin-left:0;" class="" href="docs/android-building-from-source.html">Building React Native from source</a></li></ul></div><div class="nav-docs-section"><h3>components</h3><ul><li><a style="margin-left:0;" class="" href="docs/activityindicator.html">ActivityIndicator</a></li><li><a style="margin-left:0;" class="" href="docs/datepickerios.html">DatePickerIOS</a></li><li><a style="margin-left:0;" class="" href="docs/drawerlayoutandroid.html">DrawerLayoutAndroid</a></li><li><a style="margin-left:0;" class="" href="docs/image.html">Image</a></li><li><a style="margin-left:0;" class="" href="docs/listview.html">ListView</a></li><li><a style="margin-left:0;" class="" href="docs/mapview.html">MapView</a></li><li><a style="margin-left:0;" class="" href="docs/modal.html">Modal</a></li><li><a style="margin-left:0;" class="" href="docs/navigator.html">Navigator</a></li><li><a style="margin-left:0;" class="" href="docs/navigatorios.html">NavigatorIOS</a></li><li><a style="margin-left:0;" class="" href="docs/pickerios.html">PickerIOS</a></li><li><a style="margin-left:0;" class="" href="docs/picker.html">Picker</a></li><li><a style="margin-left:0;" class="" href="docs/progressbarandroid.html">ProgressBarAndroid</a></li><li><a style="margin-left:0;" class="" href="docs/progressviewios.html">ProgressViewIOS</a></li><li><a style="margin-left:0;" class="" href="docs/refreshcontrol.html">RefreshControl</a></li><li><a style="margin-left:0;" class="" href="docs/scrollview.html">ScrollView</a></li><li><a style="margin-left:0;" class="" href="docs/segmentedcontrolios.html">SegmentedControlIOS</a></li><li><a style="margin-left:0;" class="" href="docs/slider.html">Slider</a></li><li><a style="margin-left:0;" class="" href="docs/sliderios.html">SliderIOS</a></li><li><a style="margin-left:0;" class="" href="docs/statusbar.html">StatusBar</a></li><li><a style="margin-left:0;" class="" href="docs/switch.html">Switch</a></li><li><a style="margin-left:0;" class="" href="docs/tabbarios.html">TabBarIOS</a></li><li><a style="margin-left:0;" class="" href="docs/tabbarios-item.html">TabBarIOS.Item</a></li><li><a style="margin-left:0;" class="" href="docs/text.html">Text</a></li><li><a style="margin-left:0;" class="" href="docs/textinput.html">TextInput</a></li><li><a style="margin-left:0;" class="" href="docs/toolbarandroid.html">ToolbarAndroid</a></li><li><a style="margin-left:0;" class="" href="docs/touchablehighlight.html">TouchableHighlight</a></li><li><a style="margin-left:0;" class="" href="docs/touchablenativefeedback.html">TouchableNativeFeedback</a></li><li><a style="margin-left:0;" class="" href="docs/touchableopacity.html">TouchableOpacity</a></li><li><a style="margin-left:0;" class="" href="docs/touchablewithoutfeedback.html">TouchableWithoutFeedback</a></li><li><a style="margin-left:0;" class="" href="docs/view.html">View</a></li><li><a style="margin-left:0;" class="" href="docs/viewpagerandroid.html">ViewPagerAndroid</a></li><li><a style="margin-left:0;" class="" href="docs/webview.html">WebView</a></li></ul></div><div class="nav-docs-section"><h3>apis</h3><ul><li><a style="margin-left:0;" class="" href="docs/actionsheetios.html">ActionSheetIOS</a></li><li><a style="margin-left:0;" class="" href="docs/alert.html">Alert</a></li><li><a style="margin-left:0;" class="" href="docs/alertios.html">AlertIOS</a></li><li><a style="margin-left:0;" class="" href="docs/animated.html">Animated</a></li><li><a style="margin-left:0;" class="" href="docs/appregistry.html">AppRegistry</a></li><li><a style="margin-left:0;" class="" href="docs/appstate.html">AppState</a></li><li><a style="margin-left:0;" class="" href="docs/asyncstorage.html">AsyncStorage</a></li><li><a style="margin-left:0;" class="" href="docs/backandroid.html">BackAndroid</a></li><li><a style="margin-left:0;" class="" href="docs/cameraroll.html">CameraRoll</a></li><li><a style="margin-left:0;" class="" href="docs/clipboard.html">Clipboard</a></li><li><a style="margin-left:0;" class="" href="docs/datepickerandroid.html">DatePickerAndroid</a></li><li><a style="margin-left:0;" class="" href="docs/dimensions.html">Dimensions</a></li><li><a style="margin-left:0;" class="" href="docs/intentandroid.html">IntentAndroid</a></li><li><a style="margin-left:0;" class="" href="docs/interactionmanager.html">InteractionManager</a></li><li><a style="margin-left:0;" class="" href="docs/layoutanimation.html">LayoutAnimation</a></li><li><a style="margin-left:0;" class="" href="docs/linking.html">Linking</a></li><li><a style="margin-left:0;" class="" href="docs/nativemethodsmixin.html">NativeMethodsMixin</a></li><li><a style="margin-left:0;" class="" href="docs/netinfo.html">NetInfo</a></li><li><a style="margin-left:0;" class="" href="docs/panresponder.html">PanResponder</a></li><li><a style="margin-left:0;" class="" href="docs/pixelratio.html">PixelRatio</a></li><li><a style="margin-left:0;" class="" href="docs/pushnotificationios.html">PushNotificationIOS</a></li><li><a style="margin-left:0;" class="" href="docs/statusbarios.html">StatusBarIOS</a></li><li><a style="margin-left:0;" class="" href="docs/stylesheet.html">StyleSheet</a></li><li><a style="margin-left:0;" class="" href="docs/timepickerandroid.html">TimePickerAndroid</a></li><li><a style="margin-left:0;" class="" href="docs/toastandroid.html">ToastAndroid</a></li><li><a style="margin-left:0;" class="" href="docs/vibrationios.html">VibrationIOS</a></li><li><a style="margin-left:0;" class="" href="docs/vibration.html">Vibration</a></li></ul></div><div class="nav-docs-section"><h3>Polyfills</h3><ul><li><a style="margin-left:0;" class="" href="docs/flexbox.html">Flexbox</a></li><li><a style="margin-left:0;" class="" href="docs/shadowproptypesios.html">ShadowPropTypesIOS</a></li><li><a style="margin-left:0;" class="" href="docs/geolocation.html">Geolocation</a></li><li><a style="margin-left:0;" class="" href="docs/network.html">Network</a></li><li><a style="margin-left:0;" class="" href="docs/timers.html">Timers</a></li><li><a style="margin-left:0;" class="" href="docs/colors.html">Colors</a></li></ul></div></div></div><div class="inner-content"><a id="content"></a><table width="100%"><tbody><tr><td><h1><a class="anchor" name="debugging"></a>Debugging <a class="hash-link" href="docs/debugging.html#debugging">#</a></h1></td><td style="text-align:right;"><a target="_blank" href="https://github.com/facebook/react-native/blob/master/docs/Debugging.md">Edit on GitHub</a></td></tr></tbody></table><div><h2><a class="anchor" name="in-app-errors-and-warnings"></a>In-app Errors and Warnings <a class="hash-link" href="docs/debugging.html#in-app-errors-and-warnings">#</a></h2><p>Errors and warnings are displayed inside your app in development builds.</p><h3><a class="anchor" name="errors"></a>Errors <a class="hash-link" href="docs/debugging.html#errors">#</a></h3><p>In-app errors are displayed in a full screen alert with a red background inside your app. This screen is known as a RedBox. You can use <code>console.error()</code> to manually trigger one.</p><h3><a class="anchor" name="warnings"></a>Warnings <a class="hash-link" href="docs/debugging.html#warnings">#</a></h3><p>Warnings will be displayed on screen with a yellow background. These alerts are known as YellowBoxes. Click on the alerts to show more information or to dismiss them.</p><p>As with a RedBox, you can use <code>console.warn()</code> to trigger a YellowBox.</p><p>YellowBoxes can be disabled during development by using <code>console.disableYellowBox = true;</code>. Specific warnings can be ignored programmatically by setting an array of prefixes that should be ignored: <code>console.ignoredYellowBox = [&#x27;Warning: ...&#x27;];</code></p><blockquote><p>RedBoxes and YellowBoxes are automatically disabled in release (production) builds.</p></blockquote><h2><a class="anchor" name="accessing-the-in-app-developer-menu"></a>Accessing the In-App Developer Menu <a class="hash-link" href="docs/debugging.html#accessing-the-in-app-developer-menu">#</a></h2><p>You can access the developer menu by shaking your device. You can also use the <code>Command⌘ + D</code> keyboard shortcut when your app is running in the iPhone Simulator, or <code>Command⌘ + M</code> when running in an Android emulator.</p><blockquote><p>The Developer Menu is disabled in release (production) builds.</p></blockquote><h2><a class="anchor" name="reloading-javascript"></a>Reloading JavaScript <a class="hash-link" href="docs/debugging.html#reloading-javascript">#</a></h2><p>Selecting <code>Reload</code> from the Developer Menu will reload the JavaScript that powers your application. You can also press <code>Command⌘ + R</code> in the iOS Simulator, or press <code>R</code> twice on Android emulators.</p><p>You will need to rebuild your app for changes to take effect in certain situations:</p><ul><li>You have added new resources to your native app&#x27;s bundle, such as an image in <code>Images.xcassets</code> on iOS or in <code>res/drawable</code> folder on Android.</li><li>You have modified native code (Objective-C/Swift on iOS or Java/C++ on Android).</li></ul><h3><a class="anchor" name="automatic-reloading"></a>Automatic reloading <a class="hash-link" href="docs/debugging.html#automatic-reloading">#</a></h3><p>You may enable Live Reload to automatically trigger a reload whenever your JavaScript code changes.</p><p>Live Reload is available on iOS via the Developer Menu. On Android, select &quot;Dev Settings&quot; from the Developer Menu and enable &quot;Auto reload on JS change&quot;.</p><h2><a class="anchor" name="accessing-logs"></a>Accessing logs <a class="hash-link" href="docs/debugging.html#accessing-logs">#</a></h2><p>To view detailed logs on iOS, open your app in Xcode, then Build and Run your app on a device or the iPhone Simulator. The console should appear automatically after the app launches.</p><p>Run <code>adb logcat *:S ReactNative:V ReactNativeJS:V</code> in a terminal to display the logs for an Android app running on a device or an emulator.</p><h2><a class="anchor" name="chrome-developer-tools"></a>Chrome Developer Tools <a class="hash-link" href="docs/debugging.html#chrome-developer-tools">#</a></h2><p>To debug the JavaScript code in Chrome, select <code>Debug JS Remotely</code> from the Developer Menu. This will open a new tab at <a href="http://localhost:8081/debugger-ui" target="_blank"><a href="http://localhost:8081/debugger-ui">http://localhost:8081/debugger-ui</a></a>.</p><p>In Chrome, press <code>Command⌘ + Option⌥ + I</code> or select <code>View</code><code>Developer</code><code>Developer Tools</code> to toggle the developer tools console. Enable <a href="http://stackoverflow.com/questions/2233339/javascript-is-there-a-way-to-get-chrome-to-break-on-all-errors/17324511#17324511" target="_blank">Pause On Caught Exceptions</a> for a better debugging experience.</p><h3><a class="anchor" name="debugging-on-a-device-with-chrome-developer-tools"></a>Debugging on a device with Chrome Developer Tools <a class="hash-link" href="docs/debugging.html#debugging-on-a-device-with-chrome-developer-tools">#</a></h3><p>On iOS devices, open the file <a href="https://github.com/facebook/react-native/blob/master/Libraries/WebSocket/RCTWebSocketExecutor.m" target="_blank"><code>RCTWebSocketExecutor.m</code></a> and change <code>localhost</code> to the IP address of your computer, then select <code>Debug JS Remotely</code> from the Developer Menu.</p><p>On Android 5.0+ devices connected via USB, you can use the <a href="http://developer.android.com/tools/help/adb.html" target="_blank"><code>adb</code> command line tool</a> to setup port forwarding from the device to your computer:</p><p><code>adb reverse tcp:8081 tcp:8081</code></p><p>Alternatively, select <code>Dev Settings</code> from the Developer Menu, then update the <code>Debug server host for device</code> setting to match the IP address of your computer.</p><h3><a class="anchor" name="debugging-using-a-custom-javascript-debugger"></a>Debugging using a custom JavaScript debugger <a class="hash-link" href="docs/debugging.html#debugging-using-a-custom-javascript-debugger">#</a></h3><p>To use a custom JavaScript debugger in place of Chrome Developer Tools, set the <code>REACT_DEBUGGER</code> environment variable to a command that will start your custom debugger. You can then select <code>Debug JS Remotely</code> from the Developer Menu to start debugging.</p><blockquote><p>The debugger will receive a list of all project roots, separated by a space. For example, if you set <code>REACT_DEBUGGER=&quot;node /path/to/launchDebugger.js --port 2345 --type ReactNative&quot;</code>, then the command <code>node /path/to/launchDebugger.js --port 2345 --type ReactNative /path/to/reactNative/app</code> will be used to start your debugger. Custom debugger commands executed this way should be short-lived processes, and they shouldn&#x27;t produce more than 200 kilobytes of output.</p></blockquote><h2><a class="anchor" name="fps-frames-per-second-monitor"></a>FPS (Frames per Second) Monitor <a class="hash-link" href="docs/debugging.html#fps-frames-per-second-monitor">#</a></h2><p>You can enable a FPS graph overlay in the Developer Menu in order to help you debug performance problems.</p></div><div class="docs-prevnext"><a class="docs-next" href="docs/testing.html#content">Next →</a></div><div class="survey"><div class="survey-image"></div><p>We are planning improvements to the React Native documentation. Your responses to this short survey will go a long way in helping us provide valuable content. 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