What Is ADB? Android Debug Bridge Explained Simply

ADB, short for Android Debug Bridge, is the tool a computer uses to talk to an Android phone, tablet or TV. With it you can install apps, read logs, copy files, run shell commands and control the screen, all from the computer. Google ships it with the Android SDK, and it is the same tool Android Studio uses under the hood every time you press Run.

A bridge with three parts

ADB looks like a single command, but it is really three programs working together:

The first time you type an adb command, the client starts the server if it is not running yet. The server then looks for devices on USB and on the network. When you run adb shell ls, the client hands the request to the server, the server forwards it to adbd on the device, and the output comes back the same way.

That is why only one program at a time should run an ADB server. If Android Studio, scrcpy and a terminal each try to own the USB connection, they fight over it and you see errors such as "device busy". The fix is usually adb kill-server or closing the other tool. More in fixing a busy or unauthorized device.

How a device lets a computer in

ADB can do a lot, so Android does not let any computer use it.

1. USB debugging must be on. It lives in Developer options, which are hidden until you tap the build number seven times. See how to enable USB debugging.
2. The device must approve the computer. Each computer has its own RSA key. The first time it connects, the phone shows "Allow USB debugging?" with that key's fingerprint. Until you tap Allow, the device is listed as unauthorized and nothing works.

You can withdraw that approval at any time with Revoke USB debugging authorizations in Developer options.

USB or Wi-Fi

ADB works over two kinds of connection:

• USB cable: the default. Fast, reliable and the easiest to set up.
• Network: either classic adb tcpip, which needs a cable once to switch the phone to port 5555, or Wireless debugging on Android 11 and newer, which pairs with a code and needs no cable at all. The differences are in adb tcpip vs Wireless debugging.

Network ADB is the only option for most TVs, which cannot be connected to a computer by USB. See how to control an Android TV with ADB.

ADB vs fastboot

People often mix the two up because they come in the same download, Android SDK platform-tools.

adb reboot bootloader is the usual bridge between them: it takes a running phone into fastboot mode. What you can do from there is in the fastboot mode guide.

How you get ADB

There are two common ways:

• Android SDK platform-tools: a free download from Google for Windows, macOS and Linux. You unzip it, add the folder to your PATH and use adb in a terminal.
• In the browser: Chrome and Edge can talk to USB devices through WebUSB, so a web page can speak the ADB protocol directly. That is how ADBKit works, with nothing to install for USB. The technical side is in what WebADB and WebUSB are.

Is ADB safe?

ADB is a debugging tool, so it gives the approved computer deep access: it can install apps, read app logs and copy files from shared storage. That is safe when the computer is yours and you know what you run. A few habits keep it that way:

• Only tap Allow for computers you trust.
• Turn USB debugging off when you no longer need it, especially on a phone you carry every day.
• Do not leave network ADB on in public or shared Wi-Fi.

Next steps

• What ADB is used for, with real examples
• The ADB commands cheat sheet
• Enable USB debugging and connect your first device