Samsung introduced the Infinity Display design language last year with the Galaxy S8 and S8+, drastically cutting down on the front bezels. To accommodate a full-screen front, the company had to eliminate the physical home button and move the fingerprint sensor to the back of the phone.
While the thin-bezel display made for a more immersive experience while using the phone, the position of the fingerprint sensor next to the camera module wasn't ideal. The S8 and S8+ sported large displays, and the tall form factor meant it was awkward to reach the fingerprint sensor.
The close proximity to the camera module also meant that users often got finger grease all over the camera sensor when they were looking to unlock the phone. The Note 8 didn't make things any easier — the phone was taller and wider than the S8+, making it even harder to reach the fingerprint sensor.
However, if the design of the Galaxy A8+ is any indication, the Galaxy S9 will feature a much more intuitive location for the fingerprint sensor. Samsung switched to the Infinity Display design for its mid-range series with the Galaxy A 2018 series, and the A8+ features a 6-inch FHD+ display. Crucially, the fingerprint sensor round the back is located below the camera module, making it easy to reach one-handed.
It's still fairly high up on the phone and isn't quite as comfortable to access as the sensor on the back of the OnePlus 5T (which also has a 6-inch 18:9 display), but it's leagues better than that of the S8+ and Note 8. This is the design that Samsung is likely to adopt in its upcoming flagship, as early CAD renders of the S9+ reveal a fingerprint sensor located below the camera unit.
The Galaxy S9+ is set to feature dual cameras at the back, and as you can see in the render above, it looks like the cameras will be arrayed vertically. That should bring the position of the fingerprint sensor even further down and make it convenient to access. The latest rumors suggest the S9+ is the only variant to pick up dual cameras, with the standard S9 is set to come with a single rear camera. However, as the regular S9 will be smaller in size, it shouldn't be any more difficult to access the fingerprint sensor from the back.
Whether the Note 9 will even feature a dedicated fingerprint sensor remains to be seen. In-display fingerprint sensors are finally viable, with Vivo set to be the first manufacturer to introduce the tech in a new variant of the X20 Plus, which is slated for an official unveil later this month.
Samsung was heavily rumored to go with an in-display sensor as a replacement for the physical home button with the S8, but the tech wasn't ready last year. While the time frame suggests it's unlikely we'll see it in the S9, we could see an in-display fingerprint sensor in the Note 9. That's just conjecture at this point, but what we can look forward to is a fingerprint sensor that's actually usable in the Galaxy S9 and S9+.
With an official unveil set for February 26 at Mobile World Congress, we're just a month away from the launch of the S9, so we should know more in the coming weeks.