Unlocking the bootloader is a fundamental step for any enthusiast who wants to gain full control of their device. Bootloader (bootloader) is a app that runs before the operating system boots and verifies the digital signature of the code it runs. By default, manufacturers set a restriction that prohibits the launch of unverified software, which makes it impossible to install custom recovery or obtain root access.
In version Android 10 Google has tightened security requirements by introducing a new partitioning scheme and enhanced system integrity checking (Verified Boot). This means that the unlocking process has become more complex and risky compared to older versions of the OS. You will have to face the complete deletion of all user data, since the encryption system is tied to the state of the bootloader.
This instruction covers the universal principles of working with the utility Fastboot, however, each manufacturer (Xiaomi, Huawei, Motorola, OnePlus) has its own unique requirements and time delays. We will analyze not only the technical side of the issue, but also the theoretical aspects so that you understand exactly what processes are happening inside your smartphone at the moment you enter the command.
Preparation of the device and necessary tools
Before starting any manipulations with the system partitions, it is necessary to ensure the stability of the connection between the computer and the smartphone. You will need a high-quality USB cable, preferably an original one, since cheap analogues often do not support data transfer in Fastbootmode. Also make sure that the battery level is at least 60% so that a sudden power outage does not turn the device into a brick.
You will need ADB and Fastboot drivers to work. On computers running Windows, they often have to be installed manually through Device Manager or using universal packages from Google. Users Linux and macOS are more fortunate: there these utilities are often available through the terminal by default or installed with one command in the package manager.
A critical step is to activate developer mode. Go to Settings → About phone and quickly click on the item "Build number"seven times. After this, a new section “For Developers” will appear in the settings menu, where you need to activate the switch USB debugging and, which is extremely important for Android 10, the item Factory unlock (OEM Unlocking).
⚠️ Attention: If the "Factory unlock" item is missing or inactive, this may mean that your telecom operator has blocked this function, or you are using a device from a region in China where unlocking is officially prohibited by the manufacturer.
☑️ Ready for unlocking
The process of entering Fastboot mode and receiving a token
After preparing the software, you need to transfer the smartphone to a special boot mode. There are two main ways to do this. The first is hardware: turn off the phone completely, then hold down the key combination (most often Volume Down + Power) and hold it until the Fastboot logo appears. The second method is software, through the terminal.
Connect the phone to the PC and enter the following instructions in the command line:
adb reboot bootloaderIf the device has successfully rebooted, you will see a screen with an image of an Android robot or a text menu. Now check the connection with the computer with the command fastboot devices. If the device serial number is displayed in the list, the drivers are installed correctly. On some models, such as Motorola or old HTC, before unlocking you need to obtain a unique token.
To do this, enter the command:
fastboot oem get_unlock_tokenThe system will issue a long string of characters, which must be copied and sent to the manufacturer's official website to receive the unlock key file. This process can take from a few minutes to several days, depending on the brand's policy.
What to do if the computer does not see the phone in Fastboot?
If the fastboot devices command returns an empty result, try replacing the USB cable or switching the port on the motherboard (use USB 2.0 ports instead of 3.0). Also check the Windows Device Manager: if there is a device with a yellow exclamation mark, you need to manually update the driver by selecting "Android Bootloader Interface" from the list of standard Google drivers.
Unlocking the bootloader directly
The unlocking itself takes seconds, but requires absolute concentration. The command depends on the manufacturer of your device. For most modern smartphones (Pixel, OnePlus, Xiaomi in global versions) the standard syntax is used.
Enter in the terminal:
fastboot flashing unlockOr, for some older devices:
fastboot oem unlockImportant: A data loss warning will appear on the smartphone screen. You will have to use the Volume buttons to navigate the menu and the Power button to confirm the selection "Unlock the bootloader". After confirmation, the device will perform a factory reset (Wipe Data) and reboot. This process may take longer than a normal download.
| Manufacturer | Unlock command | Features |
|---|---|---|
| Google Pixel | fastboot flashing unlock |
Instant unlocking, data reset. |
| Xiaomi / Redmi | Through the Mi Unlock utility | Requires account linking and waiting 168 hours (7 days). |
| Motorola | fastboot oem unlock [KEY] |
You must obtain the key on the official website. |
| OnePlus | fastboot oem unlock |
Confirmation on the phone screen, the warranty is maintained (in some regions). |
| Huawei (new) | Not officially available | Code issuing servers have been closed since 2018. |
Unlocking features on Xiaomi and Samsung devices
Smartphone owners Xiaomi face one of the strictest security policies. Official unlocking is possible only through a proprietary utility Mi Unlock Tool. You won't be able to do this simply through the console. First you need to link your Mi account in the developer settings, then log into the same account in the app on your PC.
After attempting to unlock, the system will display a message that you need to wait a certain number of hours (usually 168). Attempting to bypass this wait by relinking the account or resetting the timer often leads to blocking the account for a longer period. Wait until the timer expires, connect the phone again and complete the procedure.
The situation with Samsung is radically different. In global versions (European, American), the bootloader is easily unlocked through the Download Mode mode (pressing the Volume Down + Up buttons when connecting the cable). However, in devices intended for the US market (models with Snapdragon processors from operators), unlocking the bootloader using software methods is impossible due to hardware fuses.
⚠️ Attention: On Samsung devices, unlocking the bootloader is irreversibly triggered by a physical fuse. Knox. This means that features such as Samsung Pay, Secure Folder and Secure Folder will stop working permanently, even if you lock the bootloader back.
Possible errors and methods to resolve them
The process does not always go smoothly. One of the most common problems on Android 10 is the error FAILED (remote: Command not allowed). This happens if you forgot to enable the OEM Unlocking item in the developer settings before rebooting into Fastboot. Return to the system, enable the option and try again. Another common problem is an error when trying to use the command on devices that require the command, or vice versa. Please check the documentation for your specific model carefully. It is also possible that a message may appear indicating that the device is already unlocked.
Another common problem is the error FAILED (remote: Device is locked) when trying to use the command flashing unlock on devices that require the command oem unlock, or vice versa. Please check the documentation for your specific model carefully. You may also receive a message indicating that your device is already unlocked.
If the phone is stuck at the logo after unlocking (Bootloop), this is often due to damage to the data partition during encryption. In this case, you must enter Recovery mode again (usually Volume Up + Power) and perform a manual data reset (Wipe Data/Factory Reset). This will remove the remnants of the old encryption and allow the system to boot cleanly.
If you are using a custom kernel or a modified recovery, be sure to make a full backup of the EFS or Persist partition before unlocking. Losing these partitions can result in a broken IMEI and no network.
Consequences of unlocking and security issues
After successful unlocking, the status of the device changes. Every time you boot, you will see a warning that the bootloader is unlocked and the device is not protected. This is normal. However, it is worth understanding that the mechanism Verified Boot now works in warning mode, not blocking.
This means that an attacker who has gained physical access to your phone can theoretically flash a modified system image and gain access to your data (if the screen is not protected with a strong password). In addition, applications that use security APIs (for example, banking applications or Google Pay) may refuse to work.
To restore contactless payment, you often have to use methods to hide root access (for example, through Magisk Hide or Zygisk), but some banking applications detect the very fact of an unlocked bootloader at a deep level. In such cases, the only solution is to re-lock the bootloader, if the current firmware allows this.
Unlocking the bootloader gives complete freedom of action with the system, but irreversibly reduces the level of security of the device and may void the warranty (depending on the brand and region of purchase).
Is it possible to block the bootloader back?
Yes, in most cases this is possible using the command fastboot flashing lock or fastboot oem lock. However, this can only be done on the stock (original) firmware. If you have a custom recovery or a modified system partition installed, attempting to lock will cause the phone to stop booting (hard brick), and you will need to reflash it using special service tools.
Will the warranty be void after unlocking?
It depends on the manufacturer and the legislation of your country. In the EU and US, unlocking the bootloader is not an automatic basis for denial of warranty unless you have broken the device software. In China and some other regions, the warranty will be void immediately. Brands such as OnePlus and Xiaomi (global versions) are usually loyal, but Samsung and Huawei may refuse free repairs.
Why doesn’t the fingerprint work after unlocking?
On Android 10 and higher, biometric data encryption keys are often tied to the bootloader state. When unlocked, old keys become invalid. Usually the problem is solved by deleting all old fingerprints and re-registering them in the security settings after the first boot of the unlocked system.
What is AVB and how does it affect unlocking?
AVB (Android Verified Boot) is a mechanism for checking the integrity of the boot chain. When the bootloader is unlocked, AVB goes into a "yellow" or "orange" status mode, allowing unsigned images to be loaded, but warning the user. Complete disabling of checks (via vbmeta firmware) is required only for installing custom kernels or GSI images.
Will unlocking remove the virus, if any?
The unlocking process itself performs a data reset (Wipe), which will remove user applications, including most viruses. However, if malware has entered the system partition (which is rare without already being rooted), a simple reset will not help. Unlocking only opens up the possibility of completely flashing a clean system image, which is guaranteed to remove any software.