Unlocking the bootloader is a fundamental step for any enthusiast who wants to gain full control over their smartphone based on Android. It is this component that is responsible for safely booting the operating system and checking its integrity. While the bootloader is locked, the device will not allow the installation of custom recovery or modified firmware, limiting the user's capabilities to the framework specified by the manufacturer.
The unlocking procedure opens the door to installing custom ROMsuch as LineageOS or Pixel Experience, which can significantly extend the life of the old device or add new features. However, this action is not without risks: you can lose your warranty, encounter security problems, or even turn your phone into a brick if you act carelessly. Understanding all the nuances before starting work is critical to maintaining the functionality of the gadget.
In this article we will look in detail at what an unlocked bootloader is, how to prepare the device for the procedure and what commands need to be entered in the mode Fastboot. We will also look at differences in approaches for different brands, since manufacturers' policies on this issue differ significantly. Carefully study each step to avoid fatal errors.
Why is unlocking the bootloader needed and what risks does it carry?
The main purpose of unlocking is to remove software restrictions that do not allow the user to change system memory partitions. In the locked state, the bootloader verifies the digital signature of each bootable part of the system. If you try to install a modified kernel or recovery, the system will refuse to boot, considering the file unsafe. Unlocked bootloader Disables this check, allowing you to run any code you deem necessary.
However, freedom of action carries serious consequences for data security. When unlocked, many manufacturers automatically perform a full factory reset, erasing all user data. Moreover, some applications, especially banking and payment systems, use technology SafetyNet or its analogue Play Integrity API to check the integrity of the system. On an unlocked device, these applications may refuse to work, blocking access to online banking or contactless payment.
⚠️ Attention: Unlocking the bootloader in most cases will void the official manufacturer's warranty. If your phone is under warranty, think twice before starting the procedure, as the service center may refuse free repairs.
It is also worth considering that unlocking makes the device more vulnerable to malware. An attacker who gains physical access to the phone can theoretically download a malicious system image, bypassing the protection. For the average user, this risk is minimal, but it exists. However, the ability to install the latest version Android on an old device often outweighs these disadvantages, allowing you to continue using the gadget even after official support ends.
Preparation of the device and necessary tools
Before moving on to technical manipulations, you must carefully prepare the workplace and the device itself. You will need a computer running Windows, macOS or Linux with drivers installed for your smartphone. Without the correct drivers, the computer simply will not see the phone in Fastbootmode, and all commands will be ignored. Download the official drivers from the manufacturer's website or use the universal Google USB Driver.
The key element of preparation is installing the platform Android SDK Platform-Tools. This package contains two critical utilities: adb (Android Debug Bridge) and fastboot. The first allows you to control the device from the Android operating system, and the second works at the bootloader level. Download the archive from the official Android developers website and unpack it into a convenient directory, for example, the root of the C drive or a separate folder on your desktop.
Don't forget to make a full backup of all important data. As mentioned earlier, the unlocking process almost always initiates formatting of the data partition (userdata). This means losing photos, contacts, messages, and app settings. Use cloud services or connect your phone to a PC in file transfer mode to copy information. Also make sure that the battery is charged at least 60% so that the device does not turn off at the most critical moment.
☑️ Preparing for unlocking
Activate developer mode and OEM unlocking
The first step inside the operating system is to activate the hidden menu for developers. By default, this section is hidden from the eyes of the average user to prevent accidental changes to critical settings. To open it, go to Settings → About phone and find the item Build number (Build Number). Click on this item 7 times in a row. The system will ask you to enter your PIN code or pattern, after which a notification will appear that you have become a developer.
Now return to the main settings menu and find the new section For developers (usually it is located in the category "System" or "Advanced"). Inside this menu you need to find the OEM unlocking (OEM Unlocking) switch. Activate it. If this item is missing or inactive, your carrier or manufacturer may have blocked this feature at the firmware level. In some cases, you need to connect to Wi-Fi and wait from several hours to several days before the option becomes available.
Also in this menu you must enable the item USB debugging (USB Debugging). This will allow the computer to send commands to the device through the cable. The first time you connect the cable after enabling this option, the phone screen will ask you to confirm debugging with the computer's RSA key fingerprint. Be sure to click “Allow”, otherwise further actions will not be possible. Without this step, the utility adb will not be able to establish a connection with the device.
If the “OEM unlock” item is gray and cannot be pressed, try inserting a SIM card, connecting to Wi-Fi and waiting 7 days. On some devices (for example, Huawei or older Samsung models), this option may be completely removed from the menu.
Entering Fastboot mode and checking bootloader status
After preparing the software and phone settings, you need to put the device into a special boot mode - Fastboot (also known as bootloader mode). The login method depends on the model: most often you need to turn off the phone and then hold down the combination of buttons Volume Down and Power at the same time. For some manufacturers, for example OnePlus or Xiaomi, the combinations may differ, so it is worth checking the information in the documentation for the specific model.
Connect the phone to the computer via the original USB cable. Open a command prompt (Terminal on macOS/Linux or PowerShell/CMD on Windows) in the folder where Platform-Tools is installed. Enter the command to check the connection:
adb devicesIf a device with a serial number and status appears in the list device, the connection was established successfully. If the status is unauthorized, check the phone screen and confirm debugging. If the device does not appear at all, reinstall the drivers or try a different USB port. Next, enter the command to reboot into bootloader mode:
adb reboot bootloaderAfter the reboot, an Android robot image or a text menu should appear on the phone screen. Now check the current status of the bootloader with the command:
fastboot oem device-infoIn response you will receive information about the locking status. Look for the line Device unlocked: false or (un)lockbootloader: unlock is not allowed. This confirms that the bootloader is still locked. If you see a "waiting for device" error message, the Fastboot drivers are not installed or the cable is faulty. Make sure you are using Fastboot mode and not Download Mode (which is used by Samsung for flashing via Odin).
| Brand | Unlock command | Features | Reset data |
|---|---|---|---|
| Google Pixel | fastboot flashing unlock |
Confirmation required on the screen | Yes |
| Xiaomi / POCO | Through the Mi Unlock utility | You need to link your account and wait 7-30 days | Yes |
| OnePlus | fastboot oem unlock |
Simple procedure, the warranty is partially preserved | Yes |
| Sony | Through the Sony website + unlock code | Requires obtaining a unique code on the website | Yes |
| Moto | fastboot oem unlock [code] |
The code is obtained on the official Motorola website | Yes |
Unlocking process: commands and actions
The process itself unlocking depends on the specific manufacturer's policy. For devices of the line Google Pixel and many other “pure” Android smartphones, the standard command is used fastboot flashing unlock. Pay attention to the word flashing: in new versions of Android, the command syntax has changed, and the old command oem unlock may not work. After entering the command, a data loss warning will appear on the phone screen. Use the volume buttons to navigate and the power button to confirm your choice Unlock the bootloader.
For device owners Xiaomi and Redmi the situation is more complicated. Standard Fastboot commands do not work directly here. You will need the official utility Mi Unlock Tool on your computer. After logging into your Mi account inside the app and connecting your phone in Fastboot mode, the utility will check the binding status. If you linked your account less than 7 days (and sometimes up to 30 days) ago, the app will inform you that you need to wait. Trying to bypass this limitation by resetting the timer often results in longer wait times.
⚠️ Attention: When unlocking Samsung devices through Download Mode (using the combination of Volume Down + Volume Up + Connect Cable buttons), the physical Knox fuse is triggered. This permanently changes the eFuse bit, and features like Samsung Pay and Secure Folder will stop working permanently, even if you lock the bootloader again.
Once the command is completed successfully, the device will automatically reboot and begin the data wipe process. The screen may go blank, the phone may reboot several times - this is normal behavior. Do not unplug the cable or press any buttons at this time. Once the system boots up, you will see the standard welcome setup menu, just like on a new phone. The bootloader status can be checked again via Fastboot, now it should be displayed as Device unlocked: true.
What to do if the command returns the error "Command not allowed"
This error often occurs on devices purchased from carriers (carrier locked). Operators block the ability to unlock the bootloader. In this case, random methods will not work, and you will need to search for specific exploits or wait for unlocking from the operator.
Possible problems and ways to solve them
One of the most common problems is an error FAILED (remote: Command not allowed) or FAILED (device is locked). This may mean that you forgot to enable the switch OEM unlocking in the developer settings before entering Fastboot. Return to the Android system, enable the option, reboot and try again. Also make sure that the Find My Device function is not activated on the device, as it may block security changes.
Another common situation is that the computer does not see the device in Fastboot mode. In Windows Device Manager, you may see an unknown device with a yellow exclamation mark. In this case, you must manually update the driver by specifying the path to the folder usb_driver from the Android SDK. Select device Android Bootloader Interface. On macOS and Linux, driver problems are less common, but you may need to configure udev rules in Linux to allow access to the USB device without root access.
If your phone is stuck in an endless bootloop after unlocking, the boot image may have been damaged or the integrity of the partitions has been compromised. In this case, only flashing the stock firmware via Fastboot or specialized tools will help (for example Odin for Samsung, SP Flash Tool for MediaTek). It is important to download exactly the firmware version that was installed before unlocking, or a newer one, but intended for an unlocked bootloader.
Successfully unlocking the bootloader is just the beginning of the journey. To fully use the capabilities, you will need to install a custom recovery (TWRP or OrangeFox), which will allow you to install modified firmware and create full system backups (Nandroid backup).
Frequently asked questions (FAQ)
Is it possible to lock the bootloader again after unlocking?
Technically this is possible using the command fastboot flashing lock, but doing this is extremely dangerous. If the device has custom firmware or a modified boot image installed, locking the bootloader will cause the phone to stop booting (soft brick). Before blocking, you must completely restore the stock firmware with all original signatures. In addition, on some devices (for example, Sony), re-locking does not restore the operation of DRM keys.
Does unlocking the bootloader affect the operation of the camera?
On most devices, the shooting quality does not change, since the camera drivers remain the same. However, on smartphones Google Pixel and some other models, photo processing algorithms may depend on the status of the bootloader. In rare cases, when installing custom firmware, the quality of the photo may deteriorate due to the lack of proprietary image processing algorithms (GCam can partially solve this problem).
Will banking applications work after unlocking?
By default, most banking applications and Google Pay (Wallet) do not work on devices with an unlocked bootloader, since the system integrity check does not pass. However, this problem can be circumvented by using tools like Magisk (with root hiding modules and Zygisk enabled) or KSU. This will allow you to bypass security checks, but it is a constant arms race between application developers and enthusiasts.
How long does the unlocking process take?
The procedure of entering commands and rebooting takes no more than 5-10 minutes. However, for some brands, in particular Xiaomi, there is a mandatory waiting period (from 7 to 30 days) after linking the account until the server allows unblocking. For other manufacturers (Pixel, OnePlus, Moto), the process is almost instantaneous if all conditions are met.
Do you need Root access immediately after unlocking?
No, unlocking the bootloader and obtaining root access is two different processes. Unlocking only removes the ban on writing to system partitions. To obtain superuser rights, you must additionally flash a modified boot image (boot.img) with Magisk or a similar tool embedded. You can use a phone with an unlocked bootloader, but without root access.