For a number of reasons, Touch ID on Apple's mobile devices isn't always so straightforward, but there's a very effective trick to improve the sensor
Unlocking an iPhone using your fingerprint is certainly nothing new. Apple's biometric reader, in fact, is very secure, even more so than passwords. Sometimes, however, it is not always so immediate and in some cases it may not even recognize the fingerprint.
The problem is common to almost all smartphones or tablets that integrate a biometric reader. There can be a number of reasons that prevent the sensor from working properly. It's possible, for example, that the mobile device's chip didn't register all the angles of the finger. Some readers only allow you to store one fingerprint, while others allow you to use multiple fingers to unlock your phone. Apple, for example, gives the possibility to register up to a maximum of 5 fingerprints on the iPhone. Despite this, Touch ID can also act up and not respond as it should. There is a way to fix this problem.
Unless it's a serious problem due to some hardware defect, you could try recalibrating the fingerprint sensor. Don't worry, it's really very simple. Besides, it doesn't take much time. Just put your hands - or rather your finger - to the settings. The procedure we're about to outline will allow you to unlock your iPhone faster and make Touch ID more snappy. Here's how to do it.
How to improve Touch ID
As mentioned, 5 fingerprints can be registered on the iPhone. To improve the sensor, simply do the opposite, i.e. register the same fingerprint 5 times all the time. This way, you will be able to cover all angles of the finger and recognition will be faster.
Open "Settings" and then click on "Touch ID and code". You will be asked to enter a PIN. Then press on "Add a fingerprint" and you're done. Obviously, you will have to repeat the same operation several times and until 5 entries are reached.