Solve the error No bundle URL present by:

• Running the following command in your project root directory to delete the iOS build directory, and to kill other React Native sessions (assuming they're running on default port 8081) before re-building:

rm -rf ios/build/; kill $(lsof -t -i:8081); react-native run-ios

• Update your React Native workflow to avoid these error occur by combining the above combination of commands into an alias and appending it to your Bash config file .bashrc with this command:

echo "alias rni=\"kill \$(lsof -t -i:8081); rm -rf ios/build/; react-native run-ios\"" >> ~/.bashrc; source ~/.bashrc

Now you can run React Native iOS build (without worrying about some of the common red error screens of death appearing) with a simple alias shortcut:

rni

I just ran into this problem as well (first time getting started with React Native). The problem disappeared when - while an ios simulation(react-native run-ios) was running - I ran npm install and then react-native run-ios again. In the terminal window, it showed that it was bundling, and then the simulator showed the welcome screen.

Check this link for briefs after react-native init PropertyFinder line try to use npm start (This one works for me)

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UPDATE for 16.9

My port 8081 was blocked by McAfee. Using a different port directly wasn't working react-native start --port=8082 and react-native run-ios --port=8082

Tried almost all solutions given here. but anything didn't work.

        "react": "16.9.0",
        "react-dom": "^16.12.0",
        "react-native": "0.61.5",

Solution:

Searched for 8081 in Xcode and replaced all of them with 8082. Then run the same commands to build and run the app. App works smoothly

react-native start --port=8082
react-native run-ios --port=8082

This problem happens when you not allow unsecure connections via localhost, or maybe you tried to accept unsecure connections via http.

To fix this, add this on info.plist:

<key>NSAppTransportSecurity</key>
    <dict>
        <key>NSAllowsArbitraryLoads</key>
        <true/>
        <key>NSAllowsArbitraryLoadsInWebContent</key>
        <true/>
        <key>NSAllowsLocalNetworking</key>
        <true/>
    </dict>