Ultrasonic fingerprint sensors are often considered the best biometric solution on a technical level. They can be used with a wet finger, are said to be both more accurate and faster than optical sensors, and some people can even use them with thin gloves on. The problem is that they often don't work well for me. Most of the time, they don't work at all.
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I've brought up this problem several times over the years, but most recently in the Galaxy S24 Ultra review and the Google Pixel 9 Pro review. Both of these phones use the Qualcomm 3D Sonic Gen 2 ultrasonic fingerprint sensor, but Samsung's implementation is the worst for me. Nine times out of ten, the phone will not unlock using my fingerprint. The Pixel 9 series is only marginally better, something I owe to better Google software on that phone.
It wasn't until the OnePlus 13 that I found an ultrasonic fingerprint sensor that actually worked most of the time. OnePlus, Vivo, and Xiaomi now use the same Goodix ultrasonic reader which seems to be much better than Qualcomm's tech. While this was exciting enough on its own, it also gave me a new hope: maybe any old tempered glass screen protector would finally work with this sensor, too!
Unfortunately, this hasn't been the case so far.
A tempered headache
One quick search for tempered glass screen protectors on Amazon and you'll immediately notice a trend in the product names. The ones that work with ultrasonic readers will very specifically say they are ultrasonic compatible. This is a bigger problem with some phones than others, but it also means that you have to be very careful about choosing the right screen protector for the job.
When the Galaxy S24 series and Pixel 9 series launched, finding a tempered glass screen protector that worked with the ultrasonic sensors in these phones was like finding a needle in a haystack. One trick is finding a protector that uses adhesive across the entire slab of glass. Some of the cheap options just use adhesive around the edges and the air gap between the phone's display and the tempered glass protector causes big problems.
But this doesn't always fix the issue. So far, I've bought every tempered glass protector on Amazon for the OnePlus 13 — except for that stupid one with the hole in it — and none of them work with the ultrasonic fingerprint sensor in that phone. Most of them are the "adhesive around the edge" kind but one was a plain old slab of glass with adhesive across the entire back. That one also didn't work.
Tempered glass protectors have to be made a certain way to work with ultrasonic fingerprint sensors. Optical fingerprint sensors don't have this issue at all.
It's possible that this will be ironed out over time, but until then, I'm stuck using either no screen protector or just a film type that only protects against scratches. Personally, I want that extra layer of glass to protect it from drops as well as scratches.
What's most infuriating about this is that optical fingerprint sensors don't have this issue at all. I put the exact same tempered glass protectors for the OnePlus 13 on the OnePlus 12, and every single one of them immediately worked the second I applied the glass protector. Of course, these aren't made for the OnePlus 12, so they don't properly fit the screen size or shape, but they don't mess up the fingerprint sensor, either!
Some folks have had luck with getting tempered glass protectors to work on an ultrasonic fingerprint sensor-equipped phone by re-enrolling their fingerprint after applying the glass, but that never works for me. Not on the OnePlus 12, the Galaxy S24 Ultra, or the Pixel 9 Pro in my possession.
Yes, it's me (but also them)
According to one study, as many as 24% of people have a difficult to match fingerprint.
At this point, I can already hear the criticisms coming. "You're holding it wrong," "operator error," etc. etc.
No, I'm not doing anything wrong, but that doesn't mean the problem isn't me. In fact, it most likely is my fingerprints causing the issue.
While researching the topic, I came across a 2005 National Institute of Standards and Technology study that covers the topic of faulty fingerprint identification in biometrics. It breaks the results down into one of four categories:
- Sheep (subjects who are easily matched)
- Goats (subjects who are particularly difficult to match)
- Lambs (subjects exceptionally vulnerable to impersonation)
- Wolves (subjects exceptionally successful at impersonation)
The study aimed to prove (or disprove) the often-cited metric that 2% of the population cannot be identified via fingerprint at all. The results were quite different from expectations, showing that no subject could never be identified via fingerprint, but that around 6.3% were very difficult to reliably identify via fingerprint.
In fact, only 76-80% of subjects fit in the "easy to match" category, meaning it's likely that more than a few people have issues with fingerprint readers on modern smartphones regardless of the technology. One Redditor says this even happens on "$100k fingerprint reading machines," but I don't want to take Reddit as Gospel.
While I'm not ready to categorize myself as a "goat" after reading a research paper, it's clear that something with my fingerprint biology causes problems with ultrasonic sensors.
If I had any say in the matter, all phones would just ship with a capacitive fingerprint reader in the power button the way all the best foldable phones do.
I know one person who cannot use fingerprint sensors at all because her prints are too shallow. My fingerprints are also fairly shallow, and my skin is often dry, but I regularly lotion my hands — especially in the winter — so I'm not sure what else to do there.
Regardless, I've never had an issue with optical in-display fingerprint sensors' performance or accuracy. This includes performance after adding a tempered glass protector to the mix. Part of the problem lies with my biology, but the other part is the technology many modern Android phones are using to read those prints.
If I had any say in the matter, all phones would just ship with a capacitive fingerprint reader in the power button the way all the best foldable phones do. These have no widespread issues with reading, are in a far more comfortable and ergonomic position than one awkwardly placed under the glass, and are never blocked by a case or screen protector because they're in the power button.
I'd even be fine with the sensor on the back of the phone like all Pixel phones had before the Pixel 6, but I have a feeling I won't get my way here.
