Android Studio 3.0 Execution failed for task: unable to merge dex

android android-studio-3.0 build-error

For Cordova based project, run cordova clean android before build again, as @mkimmet suggested.

android android-studio-3.0 build-error

This error happens when you add an external library which may not be compatible with your compileSdkVersion .

Be careful when you are adding an external library.

I spent 2 days on this problem and finally it got solved following these steps.

Make sure all your support libraries are same as compileSdkVersion of your build.gradle(Module:app) in my case it is 26.
In your defaultConfig category type multiDexEnabled true. This is the important part.
Go to File | Settings | Build, Execution, Deployment | Instant Run and try to Enable/Disable Instant Run to hot swap... and click okay
Sync Your project.
Lastly, Go to Build | click on Rebuild Project.
Note: Rebuild Project first cleans and then builds the project.

android android-studio-3.0 build-error

Try to add this in gradle

    android {      defaultConfig {        multiDexEnabled true        }   }

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