Xiaomi Mi 9T and Mi 9T Pro series are well-deservedly considered legends in the Android world, but their openness carries risks. Many users, experimenting with superuser rights or custom firmware, sooner or later come to the need to return the device to its original state. The process of locking the bootloader is a critical step to restore factory warranty, improve data security and, often most importantly, for the correct operation of banking applications and Google Pay services.
Now, a locked bootloader is the state of any modern Android device when you leave the factory, and it checks the digital signature of the system partitions when you start, preventing you from running the modified code. If you unlocked it before, Xiaomi and Google label the device as "doubtful," which limits the functionality of NFC and some multimedia codecs. Returning to the effluent state requires accuracy and strict adherence to the algorithm of actions.
In this article, we will discuss in detail the process of back-close Bootloader on the Mi 9T model. We will discuss the preparation, risks associated with data loss, and the step-by-step procedure for firmware stock image. Remember that the procedure of locking the bootloader on the Xiaomi Mi 9T irreversibly deletes all user data, so creating a full backup is a prerequisite before starting work. Do not neglect this rule, as it will be impossible to restore photos or correspondence after formatting without a backup.
Why you need to lock the bootloader on Xiaomi Mi 9T
The main reason Xiaomi Mi 9T owners decide to lock the bootloader back is to use mobile banking. Modern banking applications like SberBank, Tinkoff and others use SafetyNet (or its replacement Play Integrity API) mechanisms to verify the integrity of the operating system. If the bootloader is unlocked, the application sees a vulnerability and refuses to work, blocking transfers and payments. Shutting down the bootloader returns security status to normal.
The second important aspect is the security of personal data: the unlocked bootloader allows anyone who gets physical access to your phone to reset the screen lock password and access files by connecting the device to a computer. The locked one prevents such attacks, since it can only be downloaded with the original, manufacturer-signed system, which is especially true in the case of loss of the gadget or theft.
⚠️ Note: After blocking the bootloader, you will lose the ability to install custom Recovery (TWRP) And modify the system partitions without re-unblocking them, make sure you don't really need root rights anymore.
In addition, some MIUI features, such as Xiaomi’s Find My Device, may not work properly or be completely disabled on open-loader devices. The lock restores the full functionality of the Mi Cloud ecosystem. It is also worth noting that when a device is resold, a locked bootloader increases its liquidity, since the buyer can be sure that there are no hidden modifications to the system.
Preparation of the device and necessary tools
Before you start technical manipulations, you need to prepare a software environment. You need a Windows computer (preferably version 10 or 11), which is in good working order. USB-A high-quality cable with a high-quality shielding and an original or proven power supply. 9T It is important to use the port USB 2.0 or 3.0 on the motherboard, avoiding front panels of the PC case, where voltage drawdowns are possible.
The computer must have an ADB and Fastboot driver package installed, without which the computer will not be able to properly interact with the phone in boot mode, and you will need the latest Mi Flash Tool, which can be downloaded from the official MIUI forum or proven resources like 4PDA. Make sure that antivirus software does not block the work of Xiaomi drivers.
The most important thing is battery power. The process of firmware and lock can take from 10 to 30 minutes. If the phone turns off at the time of writing critical partitions, the device can turn into a "brick." Charge the Mi 9T to at least 60%, ideally up to 100%. Also remember to turn off any background downloads on the PC so as not to interrupt the flow of data.
- 📱 Smartphone Xiaomi Mi 9T with unlocked loader and enabled debugging USB.
- 💻 PC with Windows and installed drivers Qualcomm and Xiaomi USB Driver.
- 🔌 Original. USB Type-C cable (data support required).
- 📂 Downloaded stock firmware (Fastboot) ROM) For your model (Davinci or Davinciin).
Search and preparation of stock firmware (Fastboot ROM)
To lock the bootloader, it is not enough to just press the button in the menu; you need to flash the device with clean stock firmware in Fastboot mode. The key here is choosing the correct version of the software. For Xiaomi Mi 9T (codename davinci) and Mi 9T Pro (davinciin), firmware is not compatible. Using the wrong image will lead to errors or inoperability of communication modules.
The firmware should be Fastboot ROM type (it has the extension.tgz), not Recovery ROM (extension.zip). The Recovery file is designed to be updated through the update menu in the phone itself and does not contain tools to work with the bootloader. download images only from official Xiaomi servers or trusted mirrors to eliminate the risk of malicious code introduction.
Once the archive is loaded, it needs to be unpacked, and it's important that the path to the firmware folder is free of Cyrillic characters and spaces, because the Mi Flash utility may not properly process the path. C:\XiaomiROM\davinci_global.
| Parameter | Description | Importance |
|---|---|---|
| Type of firmware | Fastboot ROM (.tgz) | Critically. |
| Region | Global / EU / Russia / China | Tall. |
| Android version | Must be newer or equal to the current | Medium |
| File size | Usually 3.5 - 4.5 GB | For verification |
How to check the compatibility of the firmware?
Step-by-step instructions for blocking the loader
The locking process is done through the Mi Flash Tool. Run the program on behalf of the administrator. In the main window, click the Refresh button; if the drivers are installed correctly, your smartphone with the serial number should appear in the list. If the device does not appear, check the cable and connection mode.
Next, select the path to the unpacked firmware. Press the "Select" button and specify the folder where the image file is located. Pay attention to the bottom of the program window: there are three radio buttons. To completely lock and clean the data, select the "Clean all and lock" option. It is the presence of the word "lock" in the mode name that ensures that after the firmware is closed.
Turn the phone into Fastboot mode. Turn off the Mi 9T, then press the Volume Down and Power buttons at the same time. Hold them until the image of a hare repairing an android appears or the words "FASTBOOT." Connect the phone with a cable to your PC. In the Mi Flash Tool, press the "Flash" button. The process will take a few minutes, the progress bar will be filled with green.
☑️ Checklist before firmware
Once the process is complete, the phone will automatically restart. The first boot after locking the bootloader and changing the firmware type can last up to 10-15 minutes. The Mi logo, then Android, then Mi again may appear on the screen. Don't panic or try to turn off the device at this point - the initial partition setting is going on.
Solving problems and errors in firmware
During the locking process, users of Xiaomi Mi 9T can encounter various errors, one of the most common is “Missmatching image and device.” This means that you are trying to flash firmware from one model (eg Global) to a device with another regional reference or vice versa, or the bootloader version does not match the system version, in which case you need to download another firmware version that strictly corresponds to the current state of the phone or newer.
Another common problem is the error in the stage. 15-20% or 90%. This is often associated with instability. USB-Use a cable or port. Try reconnecting the cable to another port (preferably) USB 2.0 You can also temporarily disable the antivirus, which can block the recording of system files.
⚠️ Note: If after blocking the bootloader, the phone goes into an endless restart (bootloop) and shows the Mi logo, an incompatible version of the software may have been stitched. In this case, you will need to re-unlock the bootloader (if it is still possible) and firmware through the bootloader. EDL-regime.
If the Mi Flash Tool is not enough space, it means that the firmware you choose requires more space than the partitions you have, or you are trying to roll back to an older version of Android without first unlocking (Downgrade protection). 9T rollback 9 Android 11/12 Unlocked loader is not possible.
💡
Use short cables (up to 1 meter) for firmware. Long cables often have high resistance, which leads to a voltage drop at a critical point in data writing.
Status check and restoration of warranty seal
Once the system is successfully booted, you need to make sure that the bootloader is indeed locked, and the easiest way is to go back to Fastboot mode (turn off, pinch Down + Power). The screen at the bottom should be that LOCKED is orange or blue, and if it says UNLOCKED, then the procedure failed or the "Clean all" option was chosen without the word "lock".
You can also check the status through the engineering menu. Dial the code ##6484## (CIT), go to Version Information or CI Version. It should display the lock status. In addition, the About Phone -> MIUI version menu can also display the status of the bootloader when you repeatedly click on the logo.
The important thing is to check the work of Google Pay and banking applications. If the status of LOCKED, but the applications still swear on security, there may be traces of root rights in the system. In this case, you may need a full reset (Wipe Data) via Recovery. To log into Recovery on a phone that is turned off, press Volume Up + Power and select Wipe Data.
💡
The presence of the LOCKED label in Fastboot mode and the successful launch of banking applications are the main indicators of the successful locking of the bootloader on the Xiaomi Mi 9T.