ADB device offline error
'Device offline' means ADB can see your phone but can't talk to it — usually because the daemon got into a bad state. The fix is almost always a hard restart of the ADB server.
Quick answer
Run adb kill-server followed by adb start-server, then unplug and replug your USB cable. If the device still shows offline, reboot the phone — the ADB daemon on the device side gets stuck and only a reboot clears it.
What "offline" means (and what it doesn't)
When adb devices lists your phone with the state offline instead of device — or you see "error: device offline" or "device could not be connected (state=offline)" — ADB has found the phone over USB but the device-side daemon has stopped answering. The hardware link is fine; it's a stuck handshake, not a dead cable or port. (Compare "device not found", where ADB sees nothing at all, and "unauthorized", where you simply haven't approved the PC yet.) Because it's a daemon state, the fix is almost always to restart that daemon — on the PC first, then on the phone.
The 30-second fix
Restart the ADB server and re-seat the connection — this clears the great majority of offline states:
- Run
adb kill-server, thenadb start-server. - Unplug the USB cable and plug it back in.
- Watch the phone for an "Allow USB debugging?" prompt and tap Allow.
- Run
adb devicesagain — the state should now readdevice.
With the state back to device, normal commands work again — for example, installing an APK from your PC in a single line.
If it persists — reboot and re-authorize
Reboot the phone. Yes, really — the ADB daemon on the device side gets stuck and a reboot is often the only thing that clears it. If it returns offline after the reboot, revoke the trust in Developer options → Revoke USB debugging authorizations, reconnect, and accept the fresh prompt. Updating to the latest platform-tools fixes the common case where an old ADB client can't talk to a newer Android build.
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Keeps dropping offline, or offline over Wi-Fi
If the device flips between online and offline, the culprit is usually a flaky cable, a front-panel USB port, or Windows power management. Use a data-grade cable in a rear USB 2.0 port and disable USB selective suspend in Windows power options. Over wireless ADB, "offline" shows up when the phone sleeps or switches networks — keep the screen awake, stay on one network, and run adb connect <ip>:5555 to reconnect.
Mismatched ADB versions
If you have two ADB binaries on your PATH (one from Android Studio, one from a separate install), they fight and can leave a device wedged offline. Run where adb to find every copy, and remove the older one so a single, current platform-tools is in charge.
Frequently asked questions
"Offline" means ADB connected to your device but the device-side daemon stopped responding to commands. It's different from "unauthorized" (you haven't tapped Allow on the phone) and "device not found" (ADB can't see the device at all). The usual causes are a stuck ADB daemon, a USB cable that dropped its data link, or an ADB client that's older than the device's build.
Restart the ADB server with adb kill-server then adb start-server, unplug and replug the USB cable, and re-tap "Allow USB debugging" on the phone. If it's still offline, reboot the phone — the device-side daemon can hang and only a reboot clears it. Updating to the latest platform-tools resolves version-mismatch cases.
Repeated offline drops are almost always a flaky cable, a front-panel USB port, or Windows power management cutting the link. Use a known-good data cable in a rear USB 2.0 port, and disable "USB selective suspend" under Windows power options. On the phone, toggling USB debugging off and back on re-establishes the handshake.
It means ADB sees the device entry but its state is offline instead of device — the USB connection exists, but the authorization handshake didn't complete. Restart the server and accept the RSA prompt; if no prompt appears, revoke USB debugging authorizations in Developer options and reconnect.
No. Offline is a software handshake state between ADB and the device, not hardware damage — your phone and files are fine. Once the daemon restarts and you re-authorize the connection, the status returns to device. If it only ever happens with one cable, that cable is likely charge-only and should be swapped for a data cable.
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