Failed to resolve: com.android.support.design:25.4.0

Important: The support libraries are now available through Google's Maven repository. You do not need to download the support repository from the SDK Manager. For more information, see Support Library Setup.

Step 1: Open the build.gradle file for your application.

Step 2: Make sure that the repositories section includes a maven section with the "https://maven.google.com" endpoint. For example:

allprojects {
    repositories {
        jcenter()
        maven {
            url "https://maven.google.com"
        }
    }
}

Step 3: Add the support library to the dependencies section. For example, to add the v4 core-utils library, add the following lines:

dependencies {
    ...
    compile "com.android.support:support-core-utils:25.4.0"
}

A more updated version of the answer of "Bhavesh Patadiya" :

1. In your project build.gradle file, add google() into the repositories blocks:

   repositories {
       jcenter()
       google()
   }
   

2. Update the same file with a newer Gradle version:

   classpath 'com.android.tools.build:gradle:2.3.3'
   

3. If the above cause you new issues or the same issue, exit Android-Studio, and delete the "gradle" folder/s (maybe also ".gradle" folder) and the "build" folder and sub-folders, and then open Android-Studio again.

Always keep appcompact version and support lib versionssame, so change com.android.support:design:25.4.0 to com.android.support:design:25.3.1