Everything You Need to Know About Fingerprint Sensors on Android

By Ryan Whitwam

Some phones perform better than others, but they all have strong points.

Android phones started sporting fingerprint sensors years ago, but the technology was still too early to make a big impact on the experience. After Apple introduced Touch ID on the iPhone, Android OEMs came back to fingerprint reader tech with renewed interest. Thanks to improved hardware, it has become a feature people actually want on Android. However, not all fingerprint readers on Android are created equal. Here's how they differ, and how users can maximize their usefulness today.

Speed and accuracy

Having a phone that unlocks quickly from a fingerprint is good, but sometimes accuracy is actually preferable. One of the primary things to consider here is how you wake up the phone. Take the Nexus phones for example -- you can tap the rear-facing Nexus Imprint sensor to wake and unlock the phone. It happens quickly and is highly accurate. If you want to see the lock screen without unlocking, there's a dedicated power button on the side. The Honor 5X is similar, and works quite well.

The G5, on the other hand, has the power button combined with the rear-facing sensor. If you press the button so you can just check your notifications on the lock screen, it's probably going to read your fingerprint because the sensor is very fast to react. That might not be what you want in this scenario because fast doesn't mean accurate. The G5's sensor misses more often than the Nexus phones, so you may get a rejected print. When that happens, you have to lift your finger and tap again should you decided to unlock. It's annoying. So here, you might prefer the sensor was slower and more accurate. The V10 suffers from the same issue, but it seems a bit more accurate to me at least.

Samsung didn't change much this year in the Galaxy S7. If you've used a GS6, it's pretty much the same. The sensor is reasonably accurate, but a little on the slow side. It also takes a long time to learn prints compared to the Nexus phones and G5. HTC's front-facing sensor is actually much nicer than Samsung's this generation. It's faster, recognizes prints in almost any orientation, and can wake the phone up with a quick tap as opposed to pressing a physical button. The OnePlus 2 is way behind the other front-facing sensors in terms of speed and accuracy. The button also has general sensitivity issues. I like that all three of these phones have separate power buttons in case I just want to see the lock screen notifications.

From my time with the Sony Xperia Z5, I was not terribly impressed with the accuracy (I used the Compact and Premium for a few weeks). It would sometimes take two or three attempts to get the phone to read correctly. It also took just a beat too long for the sensor to read after pressing the power button to wake up. This is admittedly hard to get right, but sometimes the Z5 just doesn't read at all. There are issues here. Frankly, the much cheaper Nextbit Robin has a better side-mounted sensor. The button is recessed and not as easy to press, but the sensor is accurate and won't blast out a failed read the instant you wake the phone up to glance at your notifications.

Placement

We have thankfully moved past the era of swipe-based fingerprint scanners like the one used in the Galaxy S5. Everything is a tap sensor like the iPhone debuted back in 2013. There are three different locations you might find the sensor on Android phones -- on the front below the screen, on the back under the camera module, and on the right edge.

Each location has its own charm, but some make more sense than others, in my opinion. You also have to take into account where the power button is. Did the OEM build the sensor into the power button or not? You're going to unlock your phone dozens of times per day, so this is the sort of thing you should think about when choosing a phone.

Samsung is probably the first OEM that comes to mind when you ponder the front-facing fingerprint sensor. It's built-into the clicky home button on all of its phones (Galaxy S7, Note 5, etc.). It's not always the most comfortable spot for a sensor. It's not a natural place for your finger to rest when you pick up the phone, but you'll probably be able to manage well enough. HTC and OnePlus also place a sensor here, although theirs are capacitive home buttons. Including the sensor in the home button is the primary benefit because you can wake up and unlock the phone in one tap, but there's also a dedicated power button elsewhere.

Next, we've got the right side sensors. Phones with this location include the Xperia Z5 (international) and Nextbit Robin. All phones with the right side sensor also have the sensor embedded in the power button, as far as I'm aware. This location makes a great deal of sense to me because the sensor is in a place your finger might naturally rest while picking up the phone. Some phones place the button too low, but as long as it's a bit closer to the top, you can easily hit it with your right thumb or left index finger.

Lastly, there's the rear-facing fingerprint sensor as seen on the Nexus phones, Honor 5X, LG V10, and LG G5. I like this location the most for several reasons. It's the most natural location for reading fingerprints because almost everyone places an index finger on the back of the phone. It also doesn't discriminate against one hand or the other -- the index finger of both hands will work. Having the sensor in that location also provides internal stability, a la the Motorola dimple. The only drawback is that a rear-facing sensor isn't accessible if the phone is laying flat, but it's not like the other options are very comfortable to use without picking up the phone.

Software

Fingerprint sensors are a big deal on Android because we finally have a unified framework that lets developers take advantage of them. Android 6.0 Marshmallow makes these hardware features actually useful. Of course, you have to actually run Marshmallow on a device for that to matter.

There are a few Android devices with fingerprint readers mentioned above that are still running Lollipop. That includes the Honor 5X and OnePlus 2. The V10 would have been on this list until just a few days ago too. These phones are rolling their own fingerprint code, meaning apps can't access them without using private APIs. They just aren't very useful until then. Although, Huawei's Honor 5X does have a neat trick with gestures on the fingerprint sensor (eg. swipe down to open notifications), and it's not clear if that will work on Marshmallow.

Samsung actually has its own set of public APIs for fingerprints, but its newest devices support Marshmallow APIs too. It had fingerprint sensors for a few years before Google implemented them, so there are actually a number of apps that added support. This shouldn't complicate matters anymore, but Samsung does still use its private APIs for things like Samsung Pay.

If you do have Android 6.0, you'll find that a growing number of apps have support for fingerprint security including Chase, Chipotle, LastPass, Focus, State Farm, and Bank of America. You need to have your fingerprints added to the system security menu as it keeps the data locked up tight. The apps just plug into the Marshmallow APIs and your fingerprint data is never transferred off the device.

There are also a few things you can do in Google's ecosystem with your fingerprints added to a Marshmallow phone -- unlocking the phone is just the start. The sensor will count as a valid form of authentication when adding new accounts or making a payment with Android Pay. If you venture into the Play Store settings, you can also set the fingerprint sensor to authenticate purchases. You just need to enable it and enter your password once to confirm.

Adding fingerprints to your Android phone is one of the first things you should do. Even if you're not crazy about your phone's sensor placement or accuracy, you can use smart lock to keep it unlocked most of the time. Having fingerprint unlock means you device (which is probably encrypted by default) will benefit from factory reset protection, preventing it from being used if it's stolen. Plus, you can use the sensor in apps. Even a sketchy sensor is better than typing in passwords all the time.