Instant Run is an extended behavior for the run and debug commands that enables faster debugging by not requiring a full build and reinstall for eevry change done in your app's code.
Introduced in Android Studio 2.0, Instant Run is a behavior for the Run and Debug commands that significantly reduces the time between updates to your app. Although your first build may take longer to complete, Instant Run pushes subsequent updates to your app without building a new APK, so changes are visible much more quickly.
Instant Run is supported only when you deploy the debug build variant, use Android Plugin for Gradle version 2.0.0 or higher, and set minSdkVersion to 15 or higher in your app's module-level build.gradle file. For the best performance, set minSdkVersion to 21 or higher.
After deploying an app, a small, yellow thunderbolt icon appears within the Run button (or Debug button), indicating that Instant Run is ready to push updates the next time you click the button. Instead of building a new APK, it pushes just those new changes and, in some cases, the app doesn't even need to restart but immediately shows the effect of those code changes.
Instant Run pushes updated code and resources to your connected device or emulator by performing a hot swap, warm swap, or cold swap. It automatically determines the type of swap to perform based on the type of change you made. The video above provides interesting detail about how this all works under the hood. For a quick summary of how Instant Run behaves when you push certain code changes to a target device, however, see the following table.