Fastboot Commands Explained: getvar, oem device-info and More

ADB talks to Android while it’s running. Fastboot talks to the phone one level lower — to the bootloader itself, before Android starts. That makes it the most honest source of truth about a phone’s hardware identity and lock state, and also the most dangerous tool in the platform-tools folder if you type the wrong thing.

This guide splits fastboot commands into two groups: read-only commands that are safe to run on any phone you’re inspecting, and write commands that wipe or flash and belong only on your own device. For each read-only command, you’ll see what the output means and what to watch for.

Setup: platform-tools, drivers and fastboot mode

Install fastboot

Fastboot ships in Google’s official SDK Platform-Tools alongside ADB. Unzip it and open a terminal in that folder. In Windows PowerShell, prefix commands with .\ (for example .\fastboot devices). On Windows you may also need the Google USB Driver or your phone maker’s driver before fastboot sees the device.

Enter fastboot mode

• From Android: enable USB debugging and run adb reboot bootloader.
• With buttons: power off, then hold Power + Volume Down on Pixel, Motorola, OnePlus and Xiaomi (variations exist by model).
• Samsung: Galaxy phones don’t use fastboot. They have Download mode, which talks to Samsung’s own tools, so the commands below won’t work there.

You’ll know you’re in the bootloader when the screen shows a text menu or an Android robot with options like Start, Restart bootloader and Recovery mode.

Confirm the connection

fastboot devices
fastboot devices -l

You should see a serial number followed by fastboot. If nothing appears:

• Try a different USB cable and port — charge-only cables are the number-one cause.
• On Windows, open Device Manager. An “Android” device with a warning icon needs a driver.
• On Linux, run with appropriate udev rules or sudo if your distribution requires it.
• Make sure you’re actually in fastboot mode, not recovery.

getvar: reading the bootloader’s variables

getvar asks the bootloader for a named value. It’s read-only and the best place to start.

fastboot getvar all
fastboot getvar product
fastboot getvar serialno
fastboot getvar unlocked
fastboot getvar secure
fastboot getvar version-bootloader
fastboot getvar version-baseband
fastboot getvar current-slot

• getvar all dumps every variable the bootloader exposes. The list varies enormously by manufacturer — a Pixel prints dozens, others only a handful.
• product is the device codename (for example a Pixel codename, or a Xiaomi codename). Search it on the manufacturer’s site to confirm the exact model and that it matches the listing.
• serialno should match the serial in Settings › About phone. A mismatch suggests a replaced board.
• unlocked returns yes or no — the bootloader lock state.
• secure reports whether secure boot is enforced.
• version-bootloader / version-baseband show firmware versions. Very old versions on a recent phone mean it hasn’t been updated in a long time.
• current-slot shows a or b on phones with A/B seamless updates. Either is normal.

oem device-info and get_unlock_ability

fastboot oem device-info
fastboot flashing get_unlock_ability

oem device-info (some devices)

oem commands are manufacturer extensions, so support varies. On many Qualcomm-based phones — including numerous OnePlus and older Xiaomi models — oem device-info prints lines such as:

• Device tampered: whether the bootloader detected modification.
• Device unlocked: true or false.
• Device critical unlocked: whether critical partitions (like the bootloader itself) can be flashed.
• Charger screen enabled: a harmless setting.

On a Pixel, the command typically returns an unknown-command error. That’s expected — use getvar unlocked there.

flashing get_unlock_ability

Returns 1 if the OEM unlocking switch in Developer options is on (the bootloader may be unlocked) and 0 if it isn’t. On carrier-locked phones it’s often stuck at 0 because the switch is greyed out — see OEM unlocking greyed out. For a buyer, a phone sold as “unlocked” that returns 0 here and no for unlocked is carrier-free at most, never bootloader-free.

Reboot commands

fastboot reboot
fastboot reboot bootloader
fastboot reboot fastboot
fastboot reboot recovery

fastboot reboot returns to Android — always finish an inspection with it. The others restart into the bootloader, fastbootd or recovery. reboot recovery needs a reasonably recent platform-tools release.

Commands you should NOT run on someone else’s phone

A safe fastboot inspection, start to finish

1. adb reboot bootloader (or the button combo).
2. fastboot devices — confirm one device.
3. fastboot getvar product and serialno — confirm identity.
4. fastboot getvar unlocked and flashing get_unlock_ability — confirm lock state.
5. fastboot oem device-info on supported brands — check “tampered”.
6. fastboot reboot.

Fastboot proves the hardware identity and lock state, but it can’t read the IMEI or carrier records. Dial *#06# once Android is back up. Practice in the terminal below — type help for the list, dial to see every way to read an IMEI, and imei followed by the number to validate it:

Then check the record for the brand: Google Pixel Info, OnePlus Info, Motorola Info or the Xiaomi check, plus a manufacturer and model check and a GSMA blacklist check. For the Android-side commands, read our ADB commands guide, and for what lock states mean, bootloader unlocking explained. The IMEI check guide covers the record side.

Verdict: five read-only fastboot commands tell you a phone’s codename, serial, firmware age and true lock state in under a minute. Keep it to devices, getvar, oem device-info, get_unlock_ability and reboot, and fastboot is completely safe.