This error typically occurs when trying to flash firmware or system images to an Android device (often those with Unisoc/Spreadtrum chipsets) via Fastboot while the bootloader is still locked.
To resolve this, you generally need to unlock the bootloader before the device will accept the flash command. Common Fixes
Reboot to Bootloader: Ensure you are in the actual "Bootloader" or "Fastboot" mode, not "Fastbootd" (userspace). You can try running:adb reboot bootloader
Run the Unlock Command: Once in the correct mode, try running the standard unlock command. Warning: This will wipe all data on the device.fastboot flashing unlockNote: Some devices may require fastboot oem unlock instead.
Enable OEM Unlocking: If the command fails, ensure you have enabled OEM Unlocking and USB Debugging in the "Developer Options" menu within the phone's settings.
Verify State: Check the current lock status by running:fastboot getvar all or fastboot flashing get_unlock_ability
If you are using a specific flashing tool (like SPD Upgrade Tool or a specialized ROM flasher), ensure the device is connected in the correct state and the necessary drivers are installed.
Lock and unlock the bootloader | Android Open Source Project
How to Fix "FAILED (remote: 'flashing lock flag is locked. please unlock it first')"
If you are trying to flash a custom ROM, update your firmware, or unbrick your device using Fastboot, seeing the error "FAILED (remote: 'flashing lock flag is locked. please unlock it first')" can be a major roadblock.
This error is a security safeguard. It means your device's bootloader is locked, preventing any unauthorized changes to the system partitions. Here is a straightforward guide on why this happens and how to fix it. Why is this happening?
By default, Android manufacturers ship devices with a locked bootloader. This ensures that only official, digitally signed software can run on the device. When you run a command like fastboot flash recovery or fastboot flash system, the phone checks the "lock flag." If that flag is set to "locked," the phone rejects the command to protect itself from potential malware or accidental corruption. Step 1: Enable Developer Options & OEM Unlocking
Before you can send the unlock command via your computer, you must give the phone permission to be unlocked from within the Android OS. Open Settings on your phone.
Go to About Phone and tap Build Number 7 times until you see "You are now a developer."
Go back to the main Settings menu and navigate to System > Developer Options. Find OEM Unlocking and toggle it ON. Find USB Debugging and toggle it ON. Step 2: Boot into Fastboot Mode This error typically occurs when trying to flash
Connect your phone to your PC via a high-quality USB cable and open your command terminal (CMD, PowerShell, or Terminal).
Type the following command to ensure your PC sees the phone:adb reboot bootloader
Once the phone is on the bootloader screen (usually showing a robot or text), verify the connection:fastboot devices Step 3: The Unlock Command
Warning: Unlocking the bootloader will factory reset your device. Back up all your data first.
Depending on your device manufacturer (Google, OnePlus, Xiaomi, etc.), the command may vary slightly. Try these in order: For most modern devices:fastboot flashing unlock For older devices:fastboot oem unlock
After hitting Enter, look at your phone’s screen. You will likely see a warning message asking for confirmation. Use the Volume keys to select "Unlock the bootloader" and the Power button to confirm. Step 4: Verify the Status
Once the device reboots (or you manually boot back into fastboot), verify that the lock flag is gone by typing:fastboot getvar unlocked
If it returns unlocked: yes, you can now proceed with your original flashing project without the "remote flag" error. Troubleshooting Common Issues
Command Not Found: Ensure you have ADB and Fastboot drivers installed on your PC.
Waiting for Device: This usually means your PC lacks the specific USB drivers for your phone brand. Check your Device Manager for "Android" with a yellow triangle.
Grayed Out OEM Unlocking: Some carrier-locked phones (like those from Verizon or AT&T) do not allow bootloader unlocking. In these cases, there is often no official way to bypass the "flashing lock flag."
Xiaomi Devices: You must use the "Mi Unlock Tool" and wait for a specific cooling-off period (usually 168 hours) before the flag can be flipped.
Which device model are you currently trying to unlock so I can give you the specific manufacturer tool or command?
The error "FAILED (remote: 'Flashing Lock Flag is locked. Please unlock it first!')" occurs when you attempt to flash firmware or system partitions using Fastboot while the device's bootloader is still in a "Locked" state. To resolve this, you must explicitly unlock the bootloader through a multi-step process involving device settings and terminal commands. 1. Enable OEM Unlocking Contact Manufacturer : If the device is under
Before the device will accept an unlock command in Fastboot mode, you must authorize it from within the Android operating system. Navigate to Settings > About Phone.
Tap on Build Number seven times until "You are now a developer" appears. Go to Settings > System > Developer Options. Locate and toggle on OEM Unlocking and USB Debugging.
Note: On some devices like Xiaomi, you must also bind your account under "Mi Unlock Status" and wait for a specified period (e.g., 168–720 hours). 2. Enter Fastboot Mode
Connect your phone to your computer via a reliable USB data cable.
Open a terminal or command prompt in your Android Platform Tools folder. Run the command: adb reboot bootloader.
Alternatively, power off the device and hold Power + Volume Down until the Fastboot logo (often a mascot or text) appears. 3. Unlock the Bootloader
Once in Fastboot mode, use one of the following commands depending on your device's manufacturer:
The error "FAILED (remote: '39-flashing lock flag is locked. Please unlock it first')" occurs when you attempt to flash firmware or partitions to an Android device while its bootloader is still in a "locked" state. Simply enabling "OEM Unlocking" in your phone's settings is not enough; you must also execute the specific unlock command through Fastboot. Step 1: Preparation (In Android)
Before you can run the unlock command, your phone's OS must permit it.
Enable Developer Options: Go to Settings > About Phone and tap the Build Number (or MIUI version for Xiaomi) 7 times.
Toggle OEM Unlocking: Navigate to Settings > System > Developer Options and switch on OEM Unlocking.
Enable USB Debugging: While in Developer Options, turn on USB Debugging. Step 2: Enter Fastboot Mode Connect your phone to your PC via a USB cable. Open a terminal (CMD or PowerShell) on your PC.
Type adb reboot bootloader and press Enter. Your phone should reboot to a screen showing "Fastboot" or a similar logo. Step 3: Run the Unlock Commands
Try these commands in order. Warning: This will wipe all data on your device. For most modern Android devices: fastboot flashing unlock Use code with caution. Copied to clipboard For older or specific legacy devices: fastboot oem unlock Use code with caution. Copied to clipboard If the error specifically mentions critical partitions: fastboot flashing unlock_critical Use code with caution. Copied to clipboard Technical Analysis: The "Flashing Lock Flag" Error Error
Note: Some devices will display a confirmation prompt on the phone screen. Use the Volume keys to select "Yes" and the Power button to confirm. Step 4: Troubleshoot "Unknown Command" If you receive a "Command failed" or "Unknown cmd" error:
Xiaomi/Redmi/Poco: You cannot unlock using standard fastboot commands. You must use the official Mi Unlock Tool after binding your Mi account in the Mi Unlock Status settings.
Motorola/Sony: These often require a unique "Unlock Code" obtained from the manufacturer's website.
Unisoc-based devices: Standard commands often fail; you may need a specialized tool like the TomKing62 CVE Unlocker.
Drivers: Ensure the Google USB Driver is installed. If your PC says "waiting for device," check your Device Manager to ensure the phone is recognized as "Android ADB Interface". Step 5: Verify Status To confirm your device is truly ready for flashing, run:
The error "FAILED (remote: 'flashing lock flag is locked. Please unlock it first')" occurs when you attempt to flash custom firmware or system images onto an Android device while the bootloader is locked. The bootloader is a security layer that prevents unauthorized tampering with the system. Why This Error Happens
Locked Bootloader: Most devices ship with a locked bootloader to ensure the device remains in a state produced by the manufacturer (OEM).
Security Protocol: The device rejects "flashing" commands because it hasn't been authorized to accept unofficial or modified images.
Missing OEM Settings: "OEM Unlocking" may not have been enabled in the device's developer settings before attempting the flash.
Lock and unlock the bootloader | Android Open Source Project
For MediaTek and Spreadtrum (Unisoc) devices, replacing the bootloader with an engineering version can bypass the lock flag check. This is risky and may brick your device.
Error Code: failed -remote 39-flashing lock flag is locked. please unlock it first 39--
Severity: High (Operation Aborted)
Category: Security / Write Protection
If you flash custom images, also disable Android Verified Boot (AVB) by flashing an empty vbmeta:
fastboot flash vbmeta vbmeta_null.img --disable-verity --disable-verification
