What Happens In Debug Mode

Of course, you may be wondering how you got this far in life without worrying about keys and signatures.

The Android build process creates a debug key for you automatically. That key is automatically applied when you create a debug version of your application (e.g., running the app in your IDE). This all happens behind the scenes, so it is very possible for you to go through weeks and months of development and not encounter this problem.

In fact, the most likely place where you might encounter this problem is in a distributed development environment, such as an open source project. There, you might have encountered a problem mentioned above, where a debug application compiled by one team member cannot install over the debug application from another team member, since they do not share a common debug key. You may have run into similar problems just on your own if you use multiple development machines (e.g., a desktop in the home office and a notebook for when you are on the road delivering Android developer training).

Finding Your Debug Keystore

The debug keystore is a debug.keystore file in your Android SDK data directory. This directory is not where your SDK is installed, but rather is where the tools store data unique to your account on your developer machine, such as your emulator AVDs.

This directory can be found at:

• ~/.android/ on macOS and Linux
• C:\Users\...\.android\ on Windows

(where ... is your Windows username)

Synchronizing Your Debug Signing Key

If you have a development team that, for better coordination, should all use the same debug.keystore, just pick one and copy it to all team members’ development machines, replacing their generated ones. The debug.keystore file is a binary file and should be transferable between operating systems (e.g., from Linux to Windows).