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menu__link--sublist menu__link--sublist-caret" role=button aria-expanded=false href=/docs/legacy/native-modules-intro>Legacy Architecture</a></div></ul></nav></div></div></aside><main class=docMainContainer_a9sJ><div class="container padding-top--md padding-bottom--lg"><div class=row><div class="col docItemCol_Qr34"><div class=docItemContainer_tjFy><article><div class="tocCollapsible_wXna theme-doc-toc-mobile tocMobile_Ojys"><button type=button class="clean-btn tocCollapsibleButton_iI2p">On this page</button></div><div class="theme-doc-markdown markdown"><header><h1>Debugging Native Code</h1></header><div class=banner-native-code-required><h3>Projects with Native Code Only</h3><p>The following section only applies to projects with native code exposed. If you are using the managed Expo workflow, see the guide on <a href=https://docs.expo.dev/workflow/prebuild/ target=_blank>prebuild</a> to use this API.</div> 5<h2 class="anchor anchorWithStickyNavbar_JmGV" id=accessing-logs>Accessing Logs<a href=#accessing-logs class=hash-link aria-label="Direct link to Accessing Logs" title="Direct link to Accessing Logs">​</a></h2> 6<p>You can display the native logs for an iOS or Android app by using the following commands in a terminal while the app is running:</p> 7<div class="language-shell codeBlockContainer_mQmQ theme-code-block" style=--prism-color:#FFFFFF;--prism-background-color:#282C34><div class=codeBlockTitle_kY6l>shell</div><div class=codeBlockContent_t_Hd><pre tabindex=0 class="prism-code language-shell codeBlock_RMoD thin-scrollbar" style=color:#FFFFFF;background-color:#282C34><code class=codeBlockLines_AclH><span class=token-line style=color:#FFFFFF><span class="token comment" style=color:#93a1a1># For Android:</span><span class="token plain"></span><br></span><span class=token-line style=color:#FFFFFF><span class="token plain">npx react-native log-android</span><br></span><span class=token-line style=color:#FFFFFF><span class="token plain"></span><span class="token comment" style=color:#93a1a1># Or, for iOS:</span><span class="token plain"></span><br></span><span class=token-line style=color:#FFFFFF><span class="token plain">npx react-native log-ios</span><br></span></code></pre></div></div> 8<p>You may also access these through Debug > Open System Log… in the iOS Simulator or by running <code>adb logcat "*:S" ReactNative:V ReactNativeJS:V</code> in a terminal while an Android app is running on a device or emulator.</p> 9<details class="details_IpIu alert alert--info details_jERq" data-collapsed=true><summary><strong>💡 Custom Native Logs</strong></summary><div><div class=collapsibleContent_Fd2D><p>If you are writing a Native Module and want to add custom logs to your module for debugging purposes, you can use the following method:<h4 class="anchor anchorWithStickyNavbar_JmGV" id=android-javakotlin>Android (Java/Kotlin)<a href=#android-javakotlin class=hash-link aria-label="Direct link to Android (Java/Kotlin)" title="Direct link to Android (Java/Kotlin)">​</a></h4><p>In your native module, use the <code>Log</code> class to add logs that can be viewed in Logcat:<div class="language-java codeBlockContainer_mQmQ theme-code-block" style=--prism-color:#FFFFFF;--prism-background-color:#282C34><div class=codeBlockTitle_kY6l>java</div><div class=codeBlockContent_t_Hd><pre tabindex=0 class="prism-code language-java codeBlock_RMoD thin-scrollbar" style=color:#FFFFFF;background-color:#282C34><code class=codeBlockLines_AclH><span class=token-line style=color:#FFFFFF><span class="token keyword" style=color:#c5a5c5>import</span><span class="token plain"> </span><span class="token import namespace" style=opacity:0.7>android</span><span class="token import namespace punctuation" style=opacity:0.7;color:#657b83>.</span><span class="token import namespace" style=opacity:0.7>util</span><span class="token import namespace punctuation" style=opacity:0.7;color:#657b83>.</span><span class="token import class-name" style=color:#fac863>Log</span><span class="token punctuation" style=color:#657b83>;</span><span class="token plain"></span><br></span><span class=token-line style=color:#FFFFFF><span class="token plain" style=display:inline-block></span><br></span><span class=token-line style=color:#FFFFFF><span class="token plain"></span><span class="token keyword" style=color:#c5a5c5>private</span><span class="token plain"> </span><span class="token keyword" style=color:#c5a5c5>void</span><span class="token plain"> </span><span class="token function" style=color:#79b6f2>log</span><span class="token punctuation" style=color:#657b83>(</span><span class="token class-name" style=color:#fac863>String</span><span class="token plain"> message</span><span class="token punctuation" style=color:#657b83>)</span><span class="token plain"> </span><span class="token punctuation" style=color:#657b83>{</span><span class="token plain"></span><br></span><span class=token-line style=color:#FFFFFF><span class="token plain"> </span><span class="token class-name" style=color:#fac863>Log</span><span class="token punctuation" style=color:#657b83>.</span><span class="token function" style=color:#79b6f2>d</span><span class="token punctuation" style=color:#657b83>(</span><span class="token string" style=color:#8dc891>"YourModuleName"</span><span class="token punctuation" style=color:#657b83>,</span><span class="token plain"> message</span><span class="token punctuation" style=color:#657b83>)</span><span class="token punctuation" style=color:#657b83>;</span><span class="token plain"></span><br></span><span class=token-line style=color:#FFFFFF><span class="token plain"></span><span class="token punctuation" style=color:#657b83>}</span><br></span></code></pre></div></div><p>To view these logs in Logcat, use this command, replacing <code>YourModuleName</code> with your custom tag:<div class="language-shell codeBlockContainer_mQmQ theme-code-block" style=--prism-color:#FFFFFF;--prism-background-color:#282C34><div class=codeBlockTitle_kY6l>shell</div><div class=codeBlockContent_t_Hd><pre tabindex=0 class="prism-code language-shell codeBlock_RMoD thin-scrollbar" style=color:#FFFFFF;background-color:#282C34><code class=codeBlockLines_AclH><span class=token-line style=color:#FFFFFF><span class="token plain">adb logcat </span><span class="token string" style=color:#8dc891>"*:S"</span><span class="token plain"> ReactNative:V ReactNativeJS:V YourModuleName:D</span><br></span></code></pre></div></div><h4 class="anchor anchorWithStickyNavbar_JmGV" id=ios-objective-cswift>iOS (Objective-C/Swift)<a href=#ios-objective-cswift class=hash-link aria-label="Direct link to iOS (Objective-C/Swift)" title="Direct link to iOS (Objective-C/Swift)">​</a></h4><p>In your native module, use <code>NSLog</code> for custom logs:<div class="language-objective-c codeBlockContainer_mQmQ theme-code-block" style=--prism-color:#FFFFFF;--prism-background-color:#282C34><div class=codeBlockTitle_kY6l>objective-c</div><div class=codeBlockContent_t_Hd><pre tabindex=0 class="prism-code language-objective-c codeBlock_RMoD thin-scrollbar" style=color:#FFFFFF;background-color:#282C34><code class=codeBlockLines_AclH><span class=token-line style=color:#FFFFFF><span class="token plain">NSLog(@"YourModuleName: %@", message);</span><br></span></code></pre></div></div><p>Or, in Swift:<div class="language-swift codeBlockContainer_mQmQ theme-code-block" style=--prism-color:#FFFFFF;--prism-background-color:#282C34><div class=codeBlockTitle_kY6l>swift</div><div class=codeBlockContent_t_Hd><pre tabindex=0 class="prism-code language-swift codeBlock_RMoD thin-scrollbar" style=color:#FFFFFF;background-color:#282C34><code class=codeBlockLines_AclH><span class=token-line style=color:#FFFFFF><span class="token function" style=color:#79b6f2>print</span><span class="token punctuation" style=color:#657b83>(</span><span class="token string-literal string" style=color:#8dc891>"YourModuleName: </span><span class="token string-literal interpolation-punctuation punctuation" style=color:#657b83>\(</span><span class="token string-literal interpolation">message</span><span class="token string-literal interpolation-punctuation punctuation" style=color:#657b83>)</span><span class="token string-literal string" style=color:#8dc891>"</span><span class="token punctuation" style=color:#657b83>)</span><br></span></code></pre></div></div><p>These logs will appear in the Xcode console when running the app.</div></div></details> 10<h2 class="anchor anchorWithStickyNavbar_JmGV" id=debugging-in-a-native-ide>Debugging in a Native IDE<a href=#debugging-in-a-native-ide class=hash-link aria-label="Direct link to Debugging in a Native IDE" title="Direct link to Debugging in a Native IDE">​</a></h2> 11<p>When working with native code, such as when writing native modules, you can launch the app from Android Studio or Xcode and take advantage of the native debugging features (setting up breakpoints, etc.) as you would in case of building a standard native app.</p> 12<p>Another option is to run your application using the React Native CLI and attach the native debugger of the native IDE (Android Studio or Xcode) to the process.</p> 13<h3 class="anchor anchorWithStickyNavbar_JmGV" id=android-studio>Android Studio<a href=#android-studio class=hash-link aria-label="Direct link to Android Studio" title="Direct link to Android Studio">​</a></h3> 14<p>On Android Studio you can do this by going on the "Run" option on the menu bar, clicking on "Attach to Process..." and selecting the running React Native app.</p> 15<h3 class="anchor anchorWithStickyNavbar_JmGV" 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