I've always preferred side-mounted fingerprint scanners on Android phones. However, since most new releases use under-display ones for mobile unlocking, I'd all but forgotten how handy they are.

I've been using the Samsung Galaxy Z Fold 8 for several weeks now — and loving it for all that time — and it's reminded me how great side sensors are.

This $1,900 smartphone uses the same kind of unlocking mechanism as $100 phones from a decade ago, and it's better for it. I'd love to see this kind of tool make a comeback.

The Galaxy Z Fold 8's fingerprint scanner

And why it's just so useful

The Samsung Galaxy Z Fold 8, as well as the Ultra model which I've also been using, has a side-mounted fingerprint scanner on the right edge. It works whether the phone is folded or unfolded, with the sensor in the same place on the right.

Like many side scanners I've used, it's built into the power button. So, when you press this to unlock your phone, your fingerprint is automatically scanned and recognized.

I've found it incredibly reliable. Over several weeks of use, there've only been a handful of times in which I've needed to raise and lower my finger a second time.

This fingerprint scanner is used to unlock the phone. But it's also used to validate purchases and confirm your identity when changing certain settings. I found myself using it a lot.

The only small annoyance I've found is that it's in the exact place I put my thumb when holding my phone while on a run. I keep accidentally unlocking the device while exercising.

The problem with under-display scanners

Not all of them are made equal

It's been several years since I've tested a smartphone with a side-mounted fingerprint scanner. That's not a reflection of my personal taste, but the state of the market. Basically every handset uses under-display sensors these days.

Not all under-display scanners are made equal. On a flagship phone, they'll work reliably (mostly), but that's not always the case. I often use workarounds to make them work better, and have even written articles about it.

These can sometimes struggle to pick up or recognize your fingerprint, especially if your finger is wet or dirty. You also need to ensure the screen is on for them to be active, requiring a separate power button press.

All issues are much worse on cheaper phones, as they don't get the most advanced sensors. I don't think I've used a single premium phone that is safe from these problems.

The tech makes more sense on tablets, by virtue of the way you hold them — certain models like the Samsung Galaxy Tab S10 FE use side scanners — and I find the sensor most handy when the Z Fold is unfurled.

An old-school way of doing things

Why side-mounted scanners are so rare

I understand why side-mounted fingerprint scanners aren't still commonplace, even if I have fond memories of them.

When I began reviewing smartphones, under-display scanners were new on the market, and side ones were still commonplace. A few phones with back-mounted scanners were back on the market, but I don't see those making a comeback.

I have fond memories of testing phones from Honor and Nubia with them, even though these weren't all created equal. I recall certain Sony Xperia mobiles having side sensors that barely worked.

This is because, for many users, including me, side-mounted scanners are more convenient. They're in the right place so you can tap your thumb on them when raising your phone, so your handset is awake by the time you've picked it up.

That's unlike under-display ones. I find these hard to tap accurately when I'm picking up a phone. I either have to press the button before or after I raise my device, wasting a bit of time.

It's not for everyone, but it's for some people

We all use our smartphones differently, even when it comes down to how we hold and unlock them — my mother uses her middle finger for her under-display fingerprint scanning, for some reason — and so I don't think every phone needs side-mounted sensors.

But for the same reason, it'd be good to see a return to some variation, to cater to people who prefer side (or back) fingerprint scanners. I'm convinced they should come back, given how handy they are.

This would be one of many possible workarounds for how unreliable under-display scanners can be. Even Samsung has been experimenting with solutions, even if they're simple brute-force ones.

Samsung Galaxy Z Fold 8
  •                 **SoC**
  • Qualcomm Snapdragon 8 Elite Gen 5 for Galaxy
  •                 **Display type**
  • Dynamic AMOLED 2x 120Hz
  •                 **Display dimensions**
  • 7.6-inch open / 5.5-inch closed
  •                 **RAM**
  • 12GB / 16GB