How to Manually Update Samsung Galaxy S21 Firmware Using Odin

Preparing Your Samsung Galaxy S21 for Manual Update

• 💡 Check your model number (e.g., SM-G991B) and bootloader version (SW REV) in Settings > About phone > Software information.
• ⚠️ Remember that you cannot downgrade bootloader versions; you can only install the same or a higher version.
• 🔌 Ensure your phone is powered off before proceeding to the PC steps.

PC Setup: Drivers and Odin

• 💻 Download and install Samsung USB drivers from HardReset.Info to ensure your PC recognizes the phone.
• ⚙️ Download the latest version of Odin (a flashing tool) from HardReset.Info.
• 📂 Extract both the drivers and Odin files to your desktop.

Finding and Downloading Firmware

• 🌐 Visit a reliable firmware source like sumfw.com and search for your specific model number (e.g., SM-G991B).
• 🌍 Select the correct region firmware (e.g., CO for non-branded Poland firmware) based on your location and carrier.
• ⚠️ Crucially, ensure the firmware's Android version does not represent a major jump (e.g., Android 11 to 13) unless you have backed up your data, as this can lead to data loss.
• 📦 Download the firmware package and extract its contents to your desktop.

Flashing Firmware with Odin

• 🖱️ Launch Odin and load the firmware files into the corresponding slots: BL, AP, CP, and CSC (use Home CSC to preserve data, or CSC to wipe data).
• 📲 Enter Download Mode on your S21 by holding Volume Up + Volume Down, then plugging in the USB cable while the buttons are pressed.
• 🔗 Connect your phone to the PC and wait for Odin to recognize it (a blue box should appear).
• ▶️ Click Start in Odin to begin the flashing process.
• ✅ Wait for Odin to display PASS; the phone will reboot automatically.

Post-Update Verification

• 🔌 Once the phone boots up, you can unplug the USB cable.
• 📱 Navigate to Settings > About phone > Software information to verify the updated firmware version.
• ✨ The bootloader version should remain the same or be higher, confirming a successful manual update.