05 USB connection problems

Work down this list in order. The most common cause is a charge-only cable, followed by a missing Windows driver, followed by an unauthorised device.

Before anything else: three checks

1. The cable carries data. Some cables in the box are charge-only. Swap for a cable known to transfer files.
2. The phone is unlocked and the "Allow USB debugging?" prompt was accepted. Google documents this dialog as mandatory before adb commands run (developer.android.com/tools/adb).
3. The phone's USB mode is not "charging only". Swipe down the USB notification and choose "File Transfer" for file browsing (support.google.com/android/answer/9064445).

The computer lists no device at all

• Try a different USB port, and on a desktop try a port on the back of the case. Hubs and monitor docks are common culprits.
• On Windows, open Device Manager. An entry with a yellow triangle under "Other device" or a name like "Unknown USB Device (Device Descriptor Request Failed)" means the driver, not the phone, is the problem. Install the manufacturer's driver; Google's Windows 10 steps are on developer.android.com/studio/run/oem-usb, and the manufacturer links are in ../brand-guides/.
• On Apple silicon Macs, the first connection to an unknown USB accessory raises an "Allow accessory to connect?" prompt. If it was dismissed with "Don't Allow", the port charges but carries no data; unplug, replug and choose Allow (support.apple.com/en-us/102282).
• Reboot the phone once. Cheap, and it clears a stuck USB stack.

The device shows as "unauthorized"

unauthorized means the computer is talking to the phone, but the phone has not approved this computer's key.

1. Unlock the phone and look for the "Allow USB debugging?" dialog.
2. If no dialog appears, disconnect and reconnect the cable to trigger it.
3. Still nothing: Developer options > "Revoke USB debugging authorizations", then reconnect and accept the fresh prompt (developer.android.com/tools/adb).
4. If the phone is in a locked-down work profile, the prompt may be suppressed by device policy. Test with a personal phone to confirm.

The device shows as "offline"

offline usually means a stale adb server or a negotiating USB mode change.

1. Unplug the cable, wait five seconds, plug it back in.
2. In the companion, press Refresh devices on the Phone (ADB) tab. There is no adb-console or restart button in the app: the log shows the raw error, and the Run log line is what you would quote in a bug report.
3. On the phone, toggle USB debugging off and on again.
4. If the phone switched between File Transfer and charging while you watched, the USB stack was renegotiating. Let it settle, then retry.
5. Still stuck: quit the companion, run adb kill-server then adb start-server in a terminal using the managed copy under the app's data folder (Setup shows its path), and reopen the app.

Two phones, or an emulator, are listed at once

Disconnect the extra device. If an emulator is running, close it, or tell the app which device to use. When several devices are attached, adb commands must name one, and "more than one device" is the error you will otherwise see.

What the companion shows in that case: every device appears with its serial and state, the usable one is highlighted, and it prints "More than one device is attached (serial, serial). Select the phone you want to use." Choose one with use this.

Windows: the phone connects, then disappears

• USB selective suspend can drop a phone during long transfers. In Power Options, set USB selective suspend to Disabled for the session.
• Antivirus or endpoint tools sometimes block driver installation. Re-run the driver install with the phone already connected and unlocked.
• Motorola devices ship their USB drivers inside Motorola Device Manager, and Motorola's support page notes Windows Update can supply the driver instead (en-us.support.motorola.com/app/usb-drivers/).

macOS: the phone appears, then the prompt never shows

If macOS asks "Allow accessory to connect?" and the answer was Don't Allow, the phone stays in charging mode. Reconnect and answer Allow (support.apple.com/en-au/guide/mac-help/mchlf779ae93/mac). Also make sure Developer options is actually enabled; without USB debugging the phone has no reason to prompt at all (chapter 03).

When to stop fighting the cable

Wireless ADB removes the cable, the port and the Windows driver from the equation entirely. If the phone runs Android 11 or newer and both devices share a Wi-Fi network, chapter 04 is usually faster than a driver hunt.