How to Unlock Bootloader on SAMSUNG Galaxy A21s: Step-by-Step Guide

Understanding Bootloader Unlocking

• 💡 Unlocking the bootloader is necessary for installing custom ROMs or making unauthorized changes to the Samsung Galaxy A21s.
• ⚠️ This process removes certain protection features implemented by Samsung.

Preparation Steps

• 📌 Before proceeding, back up all important data as the phone will automatically reset.
• 🔐 To prevent Factory Reset Protection (FRP) issues, navigate to Settings > Accounts and backup > Manage accounts, select your Google account, and remove it from the phone.

Enabling Developer Options and OEM Unlocking

• 🛠️ Go to Settings > About phone > Software information and tap the Build number seven times to enable Developer Options.
• ✅ Within Developer Options, enable OEM unlocking by tapping the toggle and confirming.

Entering Device Unlock Mode and Confirmation

• 🔌 Power off the phone. Then, press and hold Volume Up and Volume Down simultaneously while plugging in a USB cable connected to a PC.
• 🔵 A blue screen will appear; press and hold Volume Up to enter Device Unlock Mode.
• ❓ You will be asked to confirm bootloader unlock. Press Volume Up to proceed. Note: If it asks to lock the bootloader, it's already unlocked.
• ⏳ The phone will reset, which may take up to 5 minutes. Press the power key to dismiss any alerts and speed up the process.

Post-Unlock Setup and Verification

• ✨ After the reset, the phone will restart. It's recommended to complete the initial setup to ensure all data is read and the unlocked status is recognized by the system.
• 🔍 To verify, go to Settings > About phone > Software information, tap Build number seven times, then navigate to Developer Options. OEM unlocking should be enabled and grayed out, indicating the bootloader is unlocked.

Re-locking the Bootloader

• 🔒 To re-lock the bootloader, disable OEM unlocking in Developer Options and restart the phone. This restores protection features like FRP.