The Samsung Galaxy S10 and Galaxy S10+ are the first smartphones to launch with an ultrasonic fingerprint sensor, that is located beneath the glass. And as with any first-generation tech, it needs some work. Many have reported that the sensor is slow, and often times it cannot even recognize their finger. While other times, it's hard to find where to place your finger, since there's no circle on the screen unless you turn it on.
The good news is that there is a way to make the sensor better. Samsung has said that it will be improving the ultrasonic fingerprint sensor with future updates though, so at least there's that. But that also likely means that it won't be as secure. Here's how you can improve the sensor on your own.
Enroll Each Finger Twice
This probably sounds like a dumb thing to do, but it does actually work. While capacitive fingerprint sensors won't allow you to enroll the same fingerprint twice, this ultrasonic one will. By enrolling it twice, you're going to be able to give it more data, so that it is able to recognize you faster. It also means that you are giving it more angles, so if you are holding your phone differently, it'll still be able to recognize your finger.
Reteach the Sensor
If you're having trouble getting the sensor to recognize your fingerprint, then you may want to look at reteaching the sensor. Simply delete your fingerprint data and start over. It doesn't take too long to re-add the fingerprint(s) to your device. Just make sure to take your time and do it correctly, using the angles that you are likely to use when unlocking your phone.
The angles is actually a pretty important thing, seeing as this ultrasonic sensor does seem to be a bit finicky about trying to unlock the phone at a different angle then when you taught it. So the best way to do it, is to hold your phone like you're unlocking it, and enrolling your thumb.
Turn on Always-On Display to help with your aim
With the fingerprint sensor being under the glass, there's no way to really tell where the sensor actually is. With it in a home button or on the back of the phone, it's easy to see where it is at all times. But with it being under the display, there's no circle telling you where it is. But if you turn on the always-on display, it will show you were to place your finger, making it easier to use. And after a few days, muscle memory will take over.
The Ultrasonic Fingerprint Sensor is not perfect, and that should surprise no one. This is essentially first-generation technology, and there's bound to be some issues here and there. It should get better with a few updates from Samsung, but luckily there are some ways to improve it on your own. Of course, you can also opt to use the facial recognition on the Galaxy S10, though it isn't as secure and can't be used to login to most (if not, any) apps.