How to Lock the Bootloader on SAMSUNG Galaxy S21 FE 5G

Accessing Developer Options

• 💡 To begin, navigate to Settings, then About phone, and Software information.
• 📌 Click on the Build number seven times to enable Developer options; you may need to enter your phone's password.
• ⚠️ Ensure you are connected to Wi-Fi; if the OEM Unlocking option is grayed out, restart your phone and check again.

Preparing for Bootloader Lock

• 🔌 Shut down your phone by holding Power and Volume Down, then tap Power off.
• 🛠️ Have a USB cable ready, preferably connected to a computer for stability.
• 👆 Simultaneously press and hold Volume Up and Volume Down, then plug the cable into your phone.
• ⚡ If the screen remains blank, press and hold the Power button as well.

Locking the Bootloader

• ⬆️ Once the specific screen appears, press and hold Volume Up until the screen turns off.
• ✅ You will be prompted to lock the bootloader; select Yes by pressing Volume Up.
• ⚠️ Be aware that this process will erase all data on your phone.

Post-Lockdown Setup and Verification

• 🔄 The phone will restart and begin the data erasure process.
• 🚀 Once the phone restarts, proceed through the initial setup, connecting to Wi-Fi and skipping optional steps like account logins.
• 🔍 After setup, re-enable Developer options by tapping the Build number seven times.
• 🔒 In Developer options, you will see that OEM Unlocking is no longer grayed out; disable it and restart your phone to complete the process.