Xiaomi’s current smartphones, which run MIUI 12, offer users advanced privacy protection systems. One of the most convenient and reliable features is fingerprint biometric unlock, which allows instant access to the device, confirm payments to Google Pay or Mi Pay, and open secure applications without having to enter a complex digital password every time.
However, despite the ubiquity of the technology, many users have difficulty initially configuring or recalibrating the sensor. Sometimes the system requires re-entering data due to software failures or after a firmware update. Properly configuring biometric data is critical to ensure a balance between usability and high security of your device.
In this article, we will discuss the process of adding a fingerprint, look at the nuances of the different types of scanners and offer solutions for common errors, you will learn how to make unlocking as fast and reliable as possible, using all the features that MIUI 12 provides.
Preparing a smartphone for setting up biometrics
Before you start scanning your finger directly, you need to make sure that the device is ready to work with biometric data. First of all, your smartphone should have a lock screen in the form of a pattern lock, PIN-This is a mandatory security requirement for Android, as a fingerprint is only a convenient addition, not a complete replacement for the main method of authorization.
It is also worth checking the battery power. Although the setup process does not require much energy, suddenly turning off the device at the time of writing the finger pattern can lead to corrupted data in the protected memory area, it is recommended that the charge level be at least 20-30% before the procedure begins.
⚠️ Note: If you have previously used third-party screen locking apps or launchers, temporarily disable them. MIUI 12 and prevent the correct completion of the setting.
Make sure the scanner surface is clean. Fat traces, dust or moisture can significantly reduce the reading quality of the papillary line pattern.
☑️ Checking before setting up
Step-by-step: Adding a fingerprint
The process of adding a new fingerprint to MIUI 12 is standardized, but it has its own peculiarities depending on the location of the scanner. First, you need to go to the settings menu. Find and open the Settings section, then select Passwords and Security. In the list that opens, you are interested in the Unlock by Fingerprint option.
The system will ask you to verify your identity by entering a previously installed password or pattern lock. After successful authorization, click Add fingerprint. Animation will appear on the screen, instructing you to attach your finger to the sensor. If your device has a scanner built into the on button (side), apply your finger flat, completely covering the touch surface.
Then follow the visual cues on the screen, you'll need to repeatedly apply and tear your finger from the scanner, slightly changing the angle of inclination, the system will fill the progress bar, showing which part of the surface of the finger has already been scanned, it's important to take your time and give the device time for a vibration response after each reading.
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When scanning, try to touch the sensor with different areas of the finger pad, including the edges, which will increase the likelihood of successful unlocking, even if the finger is not perfectly flat.
After filling the scale 100%, the system will suggest adding another fingerprint or completing the setup. it is recommended to immediately add at least one reserve finger (for example, the thumb of the other hand) to be able to unlock the phone if one hand is occupied.
Features of subscreen and side scanners
Xiaomi’s line of MIUI 12-shell smartphones use two main types of sensors: capacitive side and optical subscreen. Understanding the differences between them will help set the device up more efficiently. Side scanners built into the power button are fast and work even when the screen is off.
The underscreen scanners most commonly found in flagship models require a slightly different approach, because light has to pass through the display layer, scanning and unlocking requires a slightly tighter finger than the side sensor, and the optical sensor may be less responsive to wet or fat fingers.
Technology of operation of subscreen scanners
For owners of devices with a scanner underscreen in MIUI 12, the sensitivity enhancement feature is available. If you use a protective glass, especially thick or matte, this option can be critical. You can find it along the way: Settings → Passwords and security → Unlock by fingerprint → Sensitivity enhancement.
| Type of scanner | Location. | Features of work | Moisture response |
|---|---|---|---|
| Capacitive | On-button (side) | Instant reaction, working with the screen off | Medium |
| Optical | Under the display | Requires screen brightness, a little slower | Low (requires dry hand) |
| Ultrasonic. | Under the display (rarely) | High precision, works through thick glass | Tall. |
It is worth noting that in MIUI 12, image processing algorithms from subscreen scanners have been improved compared to previous versions, which reduced the number of false denials of access.
Configuring advanced security parameters
The MIUI 12 shell provides users with flexible tools to manage biometrics. Once you add a fingerprint, you can go to the detailed settings by clicking on the gear icon or menu item next to the added finger profile, and you can delete old data, rename fingerprints (e.g., "Left Large," "Right Index") for convenience.
One of the useful features is the ability to use the fingerprint to visit hidden albums or protected folders. By activating this option, you can open confidential files with a simple touch, without entering an additional password. It also configures unlock in "in pocket" or with the screen turned off, which is especially important for side scanners.
⚠️ Attention: In-pocket unlocking may cause the screen to turn on accidentally if the phone is pressed tightly against fabrics with a specific texture.
In the same section, you can find an event log that shows the history of successful and unsuccessful unlock attempts, a useful security monitoring tool to see if someone else has tried to access your device.
Solution: If no print is added
Sometimes users are faced with a situation where MIUI 12 system refuses to save a fingerprint or the process is stuck on a certain percentage, most often the cause lies in a software security failure, in which case a simple reboot of the device helps, which clears the temporary caches of system processes.
If the reboot didn’t work, try removing all the previously saved prints and starting the process over again. Sometimes accumulated errors in old templates prevent you from correctly writing new data. It’s also worth checking for system updates, as Xiaomi regularly releases patches that fix the biometric drivers.
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If the scanner is no longer fully responsive (no vibration or backlighting), try running the diagnostics through the engineering menu by typing the code ##6484## in the phone app.
In rare cases, the problem may be hardware: the sensor plume may have left after a fall, or the sensor itself has failed. If the scanner test fails in the diagnostic menu and the reboot does not help, you may need to contact a service center.
Deletion and management of stored data
Sooner or later, you may need to delete the saved fingerprint, which may be required when you sell your phone, transfer it to another user, or simply to clean the list, go back to the Unlock by Fingerprint menu, select the profile you want, and click the Delete button, and the system will request a password confirmation.
It is important to understand that the removal of a fingerprint from MIUI 12 is instantaneous and irreversible without re-scanning. Biometric data is stored in an isolated secure module (TEE) and is not transmitted to the company's servers, so their removal is guaranteed to erase information from the device.
It is recommended to update fingerprint data periodically, at least every six months. The skin of the fingers may change (healing of small cuts, coarsening), and re-recording the current state of the papillary lines will make unlocking more stable in the long run.