Fingerprint Sensor on LG G4: Setup & Use Guide

Updated 14 November 2026 · Standard formula, shown below

This guide shows you how to set up and use the fingerprint sensor on the LG G4 (the 2015 flagship, not the G4 from other series). You’ll learn how to register your fingerprint, unlock the phone, and use it for quick app access. You’ll need your LG G4 with the latest software update installed, and your finger should be clean and dry before starting.

What You’ll Need

Your LG G4 (make sure it’s the model with a fingerprint sensor on the back, below the camera)
A clean, dry finger (the sensor is optical, so oils and dirt can affect it)
The phone’s screen unlocked and the home screen visible

Step-by-Step

Open Settings. From the home screen, swipe down from the top to open the notification shade, then tap the gear icon (Settings). Alternatively, open the app drawer and tap the Settings app.
Go to Lock screen & security. In Settings, scroll down and tap “Lock screen & security.” This may be listed as “Lock screen” on some software versions.
Select Screen lock. Tap “Screen lock” and enter your current PIN, pattern, or password if you have one. If you don’t have a lock set, you’ll be prompted to create one first—this is required for fingerprint security.
Choose Fingerprints. After setting or confirming your backup lock, tap “Fingerprints.” You’ll be asked to confirm your lock again.
Add a fingerprint. Tap “Add fingerprint” or the plus (+) icon. The phone will ask you to place your finger on the sensor (the round button on the back, just below the camera lens).
Follow the on-screen prompts. Place your finger firmly on the sensor and hold it there. The phone will vibrate or show a progress bar. Lift and repeat, slightly adjusting the finger’s position each time (move it a tiny bit up, down, left, right) so the sensor captures the full print. Continue until the progress bar fills completely.
Name the fingerprint (optional). After scanning, you can give it a label like “Right thumb” or “Index finger.” This helps you manage multiple prints later.
Test it. Lock the phone by pressing the power button, then unlock it by placing your registered finger on the sensor. It should unlock instantly.
Add more fingerprints (optional). Repeat steps 5–8 to add up to 5 different fingers. This is useful if you want to use both hands or share access with a trusted person.

Common Mistakes

Not covering the entire sensor. The sensor is small; your finger should cover it completely. If you only touch the edge, the scan will fail.
Moving your finger during the scan. Keep your finger still and flat on the sensor. Lifting or sliding it will interrupt the capture.
Skipping the backup lock. The fingerprint is only an alternative to the PIN/pattern/password, not a replacement. If you don’t set a backup, you can’t use the fingerprint at all.
Registering the same finger twice but with different angles. If you want to unlock with the same finger from different angles, you need to add it as a separate fingerprint, not assume the phone will learn it.
Forgetting to update the phone. Older software versions had fingerprint bugs. Make sure your LG G4 is running the latest available update (Settings > About phone > Update Center > Software Update).

Tips

Use a dry, clean finger. The sensor is optical and works best with a dry finger. If your hands are sweaty or greasy, wipe them on your shirt before scanning.
Scan the same finger multiple times. You can add the same finger as two or more fingerprints (e.g., “Right thumb” and “Right thumb 2”) to improve accuracy, especially if you tend to place it at slightly different angles.
Register your most-used finger first. If you’re right-handed, your right index finger is probably the most natural to reach the back sensor—register that one first.
Keep the sensor clean. Wipe the sensor gently with a soft, dry cloth occasionally to remove oil and dust that can build up.
Use it for more than unlocking. On some LG G4 software versions, you can use the fingerprint to launch the QuickMemo+ app or take a selfie (in the camera app, tap the fingerprint sensor to capture). Check your Settings > Fingerprints for these options.

Troubleshooting

Fingerprint not recognized. First, make sure your finger is clean and dry. If it still fails, delete the fingerprint and re-add it, being careful to cover the sensor fully and hold still. If it still fails, restart the phone.
Sensor not responding at all. Check if the screen is on—the sensor only works when the screen is off but the phone is not in a deep sleep. If it’s completely unresponsive, try restarting the phone. If that doesn’t help, check for a software update.
Can’t add a fingerprint. If the “Add fingerprint” option is greyed out, you likely haven’t set a backup lock. Go to Lock screen & security > Screen lock and set a PIN, pattern, or password, then try again.
Fingerprint works sometimes but not always. This is usually due to finger placement or moisture. Try adding a second print of the same finger, and make sure you’re placing your finger flat and centered.
After a software update, fingerprints are gone. Some updates reset the fingerprint data for security reasons. You’ll need to re-add them following the steps above.
Phone says “Fingerprint hardware not available.” This indicates a hardware or software issue. Restart the phone first. If it persists, back up your data and perform a factory reset (Settings > Backup & reset > Factory data reset). If the problem continues, the sensor may be damaged and require repair.

Frequently Asked Questions

How many fingerprints can I store on the LG G4?

You can store up to 5 fingerprints. You can use all 5 for the same finger (to improve accuracy) or for different fingers and people.

Can I use the fingerprint sensor to unlock apps?

On the LG G4, the fingerprint sensor is primarily for unlocking the phone. It does not support per-app locking by default. Some third-party apps may use the fingerprint API, but this is not a standard feature.

Does the LG G4 fingerprint sensor work with wet hands?

No, the optical sensor requires a dry finger. Water or sweat on your skin will cause the scan to fail. Dry your hands thoroughly before using it.

Can I use the fingerprint sensor to answer calls or take photos?

On some LG G4 software versions, you can tap the sensor to take a photo in the camera app. For calls, you can set it to answer calls by tapping the sensor in Settings > Fingerprints > Fingerprint features. This feature may vary by software version.

What happens if I forget my backup PIN/pattern?

If you forget your backup lock, you’ll need to use your Google account credentials (after 5 failed attempts) or perform a factory reset, which erases all data. It’s important to remember your backup lock.

Is the fingerprint data secure?

Yes, the fingerprint data is stored in a secure hardware module (TrustZone) and is not accessible to apps or the main system. It never leaves the device.

Method: the standard formula for this calculation, rounded as each result states. See how the calculators work or report an error.