If your Xiaomi 15's fingerprint scanner is acting up, you're in the right place. An unresponsive sensor can lock you out of your phone and apps, which is incredibly annoying. The good news is that most of the time, this is a software hiccup you can fix yourself. Let's get your fingerprint unlock working again.
Start With a Simple Restart
I'd always start with this one. A quick reboot can clear out temporary glitches in HyperOS that might be confusing the fingerprint sensor. Just press and hold the power button for a few seconds and tap restart. If it's completely frozen, a force restart is the way to go. Press and hold the power button for about 15 seconds until you feel the phone vibrate and see the Xiaomi logo appear.
Clean the Screen and Your Finger
This sounds obvious, but it's the most common fix. The Xiaomi 15 uses an under-display optical sensor, so anything on the screen or your finger can block the scan. Use a microfiber cloth to wipe the screen clean, paying extra attention to the lower area where the sensor is located. Make sure your finger is dry and free of lotion, grease, or dirt.
Check Your Screen Protector
A thick or low-quality screen protector is a prime suspect. Some protectors aren't transparent enough for the sensor's light to read your fingerprint accurately. Try removing the protector temporarily to see if the scanner starts working. If it does, you'll need to look for a protector marketed as "fingerprint-friendly" or re-register your prints after applying a new one.
Re-register Your Fingerprint
Sometimes the stored data gets corrupted. Deleting and re-adding your fingerprint often solves the problem. Head to Settings > Password & security > Fingerprint unlock. Enter your PIN, tap on the problematic fingerprint, and select "Delete".
Now, add it again. When prompted, press your finger at different angles. The phone will guide you to lift and place your finger down multiple times to capture the edges. Take your time during this process for a better scan.
Add the Same Finger Twice
For a fingerprint that's finicky, try registering it as two separate entries. Go through the setup process for "Fingerprint 1" and then immediately do it again for "Fingerprint 2" using the same finger. This gives the system more data points to recognize you from, which can improve success rates dramatically.
Update Your Software
Xiaomi frequently releases updates for HyperOS that include bug fixes for components like the fingerprint sensor. An outdated system can cause all sorts of weird behavior. Open Settings and go to About phone > HyperOS version. Tap "Check for updates" and install anything available.
After the update completes, restart your phone. It's a good habit to check for updates monthly, as they can preemptively fix issues you haven't even encountered yet.
Check for App Conflicts in Safe Mode
A recently installed third-party app could be interfering with the biometric system. Booting into Safe Mode disables all downloaded apps, letting you test the fingerprint sensor in a clean state. To enter Safe Mode, press and hold the power button until the power menu appears.
Then, tap and hold the "Power off" option on your screen. You'll get a prompt to reboot to Safe Mode. Tap "OK". If the fingerprint works perfectly in Safe Mode, you know a downloaded app is the culprit. Start by uninstalling recent apps one by one to find the offender.
Clear the System Cache
Corrupted cache files can mess with system processes, including the fingerprint service. Clearing this cache won't delete your personal data. First, power off your Xiaomi 15 completely. Then, press and hold the Power and Volume Up buttons together.
Release them when you see the Mi Recovery menu. Use the volume buttons to navigate to "Wipe data" and press the power button to select. On the next screen, choose "Wipe cache" and confirm. Finally, select "Reboot" to restart your phone normally.
Review Your Security Settings
There are a couple of settings that can affect fingerprint behavior. First, ensure "Fingerprint unlock" is actually turned on in the Password & security menu. Second, check if you have "Lock screen after timeout" or similar settings enabled, as they can sometimes conflict.
Also, if you use a work profile or any advanced device administration apps, they might enforce stricter security policies that disable biometrics. It's worth a quick look through your security settings to rule this out.
Consider a Factory Reset
This is the last resort before thinking about hardware. If a deep software issue is causing the problem, a factory reset will wipe it clean. Warning: This will erase all data on your phone. Make sure everything is backed up to your Mi Account, Google Drive, or a computer first.
To proceed, go to Settings > About phone > Factory reset. Follow the prompts to erase all data. After the phone reboots, set it up as new and test the fingerprint sensor immediately before restoring your apps. If it works now, the issue was software. If it still fails, the sensor itself may be faulty.
