How-Tos
How to Clear App Cache on Android (Manually and Across a Fleet)
Clear cache and app data on Android by hand, step by step, and how IT admins do it across many devices. Steps for Android 14 and later.
How-Tos
Fastboot Mode on Android: What IT Admins Need to Know
What fastboot mode is, how to enter and exit it, the commands IT admins use, and how to fix an Android stuck in fastboot.
- Written by
Atena LadchartabiContent writer, trio.so
- Published on
- Modified on
Fastboot mode is a pre-boot mode on an Android device, also called the bootloader screen, where a connected computer can flash partitions, read device variables and reboot the phone. It runs before Android starts, so nothing on the device, including an MDM agent, is active while it is on screen. Admins meet it when a company phone is stuck on that screen, or when a device must be reflashed.
What is fastboot mode on Android?
Fastboot is both a protocol and a command line tool. The bootloader exposes the protocol; the fastboot tool, part of Google's Android SDK Platform-Tools, talks to it over USB. Fastboot is separate from ADB. ADB talks to a running Android system; fastboot talks to the bootloader before the system starts. People search for "adb fastboot" because one repair job often uses both tools.
Samsung is the exception. Samsung phones do not use fastboot; they use Download mode and the Odin tool. The rest of this guide covers devices that use fastboot, such as Google Pixel, Motorola, OnePlus and Xiaomi.
How to enable and enter fastboot mode
You cannot "enable" fastboot as a setting. You boot into it. There are two ways.
With the keys
- Power the device off fully.
- Hold the key combination for your brand until the bootloader screen appears:
- Google Pixel and Motorola: Power + Volume Down.
- OnePlus and Xiaomi: Power + Volume Down on most models; check the maker's guide for yours.
With ADB
If the device boots and USB debugging is on, connect it and run:
adb reboot bootloader
You can reach the same screen from the recovery menu on some devices.
Set up the fastboot tool on your computer
- Download Android SDK Platform-Tools from developer.android.com for Windows, macOS or Linux and unzip it.
- On Windows, install the maker's USB driver (Google USB Driver for Pixel). On macOS and Linux no driver is needed, though Linux may need a udev rule.
- Open a terminal in the platform-tools folder, connect the device in fastboot mode and check it is seen:
fastboot devices
1A2B3C4D5E6F fastboot
The first column is the device serial number, so yours will differ. If the list is empty, the cable, port or driver is the usual cause.
Fastboot commands IT admins use
| Command | What it does |
|---|---|
fastboot devices | Lists connected devices in fastboot mode |
fastboot getvar all | Prints device variables: product, bootloader version, lock state, current slot |
fastboot reboot | Restarts the device into Android |
fastboot reboot bootloader | Restarts back into the bootloader |
fastboot flash <partition> <file> | Writes an image to a partition, for example from a factory image |
fastboot flashing unlock | Unlocks the bootloader and wipes user data |
fastboot flashing lock | Locks the bootloader again, which also wipes user data |
To leave fastboot mode, run:
fastboot reboot
Rebooting... Finished. Total time: 0.050s
The exact timing line varies by tool version and device. Older devices also accept fastboot oem unlock where flashing unlock is not supported.
How to fix an Android stuck in fastboot mode
- Use the menu. On the bootloader screen, press Volume Up or Down to cycle through options until you see Start or Reboot system now, then press Power.
- Run
fastboot rebootfrom a computer, as above. - Hold Power to force a restart. On some models, hold Power and Volume Up; check the maker's guide.
- Charge the device. A flat battery can leave a phone looping back to the bootloader.
- Check for a damaged key. A stuck Volume Down key makes the phone boot into fastboot every time.
- Reflash the factory image if the system partition is damaged. For a Pixel, use Google's factory images and flash script, or the Android Flash Tool.
Reflashing wipes the device. Back up anything that matters first, if the device still lets you.
What does unlocking the bootloader do?
Unlocking the bootloader lets you flash custom images, and it has consequences you should know before doing it on a company device:
- Data wipe. The device is factory reset on unlock, so a company-owned phone loses its work data and its management enrollment.
- Security. An unlocked bootloader weakens verified boot. Apps that check device integrity, including banking apps and some enterprise apps, can fail Play Integrity checks.
- Warranty and support. Some makers void warranty or refuse repairs on unlocked devices. Check the maker's policy.
- Prerequisite. The OEM unlocking switch in Developer options must be on, and some carriers lock it.
Most fleets never need to unlock a bootloader. Keep devices locked and use the maker's factory images for repair.
Fastboot versus managing the device
Fastboot is a repair tool. It does not manage a device. Once the device boots into Android, management takes over: you enroll it, apply policies, push apps and, if it is lost, lock or wipe it. trio.so manages enrolled Android devices, and it cannot act while a device sits in fastboot. After a reflash, enroll the device again. See Android device management.
Related reading: device admin on Android, how to whitelist an app on Android and the Android work profile.
Set up Android devices without flashing them one by one
Enroll Android devices by QR code or zero touch and apply policies from one console. Try trio.so free for 14 days.
Get Ahead of the Curve
Every organization today needs a solution to automate time-consuming tasks and strengthen security. Without the right tools, manual processes drain resources and leave gaps in protection. trio.so is designed to solve this problem, automating key tasks, boosting security, and ensuring compliance with ease.
Don't let inefficiencies hold you back.
Every organization today needs a solution to automate time-consuming tasks and strengthen security. Without the right tools, manual processes drain resources and leave gaps in protection. trio.so is designed to solve this problem, automating key tasks, boosting security, and ensuring compliance with ease.
Frequently Asked Questions (FAQ)
Have questions? We've got answers. This section covers some of the most commonly asked questions related to this topic.
A pre-boot mode in which a computer connected over USB can flash and query the device using the fastboot tool. It is also called the bootloader screen.
Choose Start in the bootloader menu, run
fastboot reboot, or hold the Power key to force a restart. If it keeps returning to fastboot, charge it, check for a stuck key, and reflash the factory image.Power off the device and hold Power + Volume Down on most devices, or run
adb reboot bootloader with USB debugging on.Run
fastboot reboot, or select Start in the bootloader menu with the volume keys and press Power.Yes.
fastboot flashing unlock factory resets the device.Related
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