How to Lock the Bootloader on the Samsung Galaxy S21 series?

The bootloader on the Samsung Galaxy S21 series plays a crucial role in the device’s functionality and security. Whether you want to lock the bootloader after testing custom ROMs or simply secure your firmware, it’s essential to know the proper steps. In this comprehensive guide, we will walk you through the process of locking the bootloader on the Samsung Galaxy S21 devices.

Before we dive into the process, let’s briefly understand what a bootloader is and why it’s important. The bootloader is a piece of software that loads the operating system on your device. It also acts as a security check, ensuring that only authorized firmware can run on your device. By default, Samsung devices come with a locked bootloader to prevent unauthorized modifications to the system.

Why Lock the Bootloader?

Locking the bootloader on your Samsung Galaxy S21 is crucial for several reasons:

1. It ensures that your device runs on the official stock firmware, providing stability and optimal performance.
2. Locking the bootloader helps protect your device from potential security risks that could arise from unauthorized firmware or custom ROMs.
3. It allows you to receive official software updates seamlessly.

Precautions Before Locking the Bootloader

Before proceeding with the bootloader locking process, it is essential to take some precautions:

1. Backup your data: Locking the bootloader will perform a factory data reset on your device. Ensure that you have backed up all your important data to prevent any loss.
2. Flash stock firmware: If you have ever modified your device in the past, it is crucial to flash the 100% stock firmware using Odin. Locking the bootloader with modified files can lead to a boot loop or a bricked device.

With these precautions in mind, let’s move on to the step-by-step process of locking the bootloader on your Samsung Galaxy S21.

Step 1: Booting into Download Mode

To initiate the bootloader locking process, we need to boot your Samsung Galaxy S21 device into download mode. Follow these steps:

1. Power off your device.
2. Connect your device to your PC or laptop using a USB cable.
3. While long-pressing the power button, simultaneously press the volume up and volume down buttons.
4. This will boot your device into download mode, indicated by a blue splash screen.

Step 2: Switching to Unlock Mode

In download mode, we will switch to unlock mode in order to re-lock the bootloader. Follow these steps:

1. In download mode, perform a long press gesture using the volume up button.
2. The device will check whether the bootloader is locked or unlocked.
3. If the bootloader is already unlocked, the device will instantly switch to lock bootloader mode.
4. If the bootloader is currently locked, the device will remain in the unlock mode.

Step 3: Confirming the Locking Process

Once you have switched to unlock mode, you need to confirm the locking process. Follow these steps:

1. A confirmation screen will appear. You can either back out by pressing the volume down button or continue to lock the bootloader.
2. Locking the bootloader will perform a factory data reset on your device. Confirm the process by pressing the volume up button.
3. The device will display a delay for a couple of seconds before the screen turns off.
4. After the screen turns off, the Samsung Galaxy S21 will reboot, performing a factory data reset as warned.

Step 4: First Boot into Android

Once the device has rebooted, it will go through the first boot into the Android system. This may take a little longer than usual due to the factory data reset. Follow these steps:

1. Be patient during the boot process and wait for the Android activation screen to appear.
2. Once you have booted back into Android, open the settings application.
3. Navigate to the “About Phone” section and tap on the “Build Number” seven to eight times to enable developer mode.
4. Developer mode is needed to access the developer options menu.

Step 5: Verifying the Bootloader Lock Status

After enabling developer mode, we can verify the bootloader lock status. Follow these steps:

1. Go back to the settings application and enter the developer options menu.
2. Check whether the OEM unlocking toggle is present.
3. Even if the toggle is present, having it on does not mean the bootloader is unlocked. It simply allows the bootloader to be unlocked.
4. To ensure that the bootloader remains locked, toggle the OEM unlocking feature off.
5. Restart the phone to use the device protection features.

Conclusion

Locking the bootloader on the Samsung Galaxy S21 series is a crucial step to ensure the security and stability of your device. By following the steps outlined in this guide, you can easily re-lock the bootloader and return it to the official stock firmware. Remember to take precautions, such as backing up your data and flashing the stock firmware, before locking the bootloader. By doing so, you can enjoy a secure and optimized experience on your Samsung Galaxy S21 device.

If you are experiencing difficulties with your device, check out our “How To” page to learn how to resolve some of these issues.