> Also whoever decided to put the fingerprint sensor on the back of the phone should be prevented from designing phones ever again.

Why? My phone has a fingerprint reader on the back, and I quite like it- I don't have to move my fingers much to use it, it's also the lock button, which makes it rather easy to "log in" to the phone.

Just tested it- less than one second to log in via finger, and it works almost all the time. (I've had motor oil on my fingers and it's still worked, not that that's a good idea...)

Also people who suggest serious consequences for failure to abide by a personal opinion should, IMO, stop talking.

The sensor on the back is out of reach when the phone is on a mount, for example the handlebar of my bicycle. I considered activating face recognition but I'll probably use the old phone as navigation device: it's got the sensor on the side. I'm using offline maps anyway and only when cycling for leisure. I'll keep my main phone in my pocket (in airplane mode, I don't want to be disturbed.)

Depending on how it's mounted...I can unlock my S8 reaching over the top of the phone where my finger is basically upside down.

I hope it means that Samsung compares the data on the whole sensor, and not that anyone can unlock it :)

Right but in my case the mount completely covers the sensor. Samsung A40 and Topeak mount. The other phone is a Sony Xperia X Compact. Maybe the Samsung is too thin to have the sensor on the side.

The fingerprint sensor on the back of the phone is something I like so much I will avoid upgrading to a device that has it anywhere else (I fear I may be using my Pixel 3 for a very long time). I think it's a genius spot for it. It's right where my finger naturally falls as I'm bringing my phone out of my pocket, so it's unlocked before my eyes ever got the screen.

Trying to use a phone with the sensor on the back just showed me how often I'm unlocking my phone while it's laying on a surface or how I always pinch the phone out of my pocket by the chin because that's all the room I have with pants that fit. Also, I can't access it when it's mounted on my bike which is such a serious showstopper I don't know how it made it out of the brainstorming phase.

I found it to be the worst place to put it.

with how big phones are these days I find it very annoying to have the lock button so far from the unlock button. i vastly prefer the scanner/unlock/lock button on the back.

Hmm, I definitely disagree based on my experiences. I think the lack of timeout with a limit on attempts is far nicer, it works reliably for me in nearly every case except sometimes in the winter (which affects other fingerprint sensors I've tried as well), and the position on the back is ideal for me in almost every position I use the phone. I can easily pull it out of my pocket and activate it one-handed without feeling like I'm holding my phone precariously.

There are good arguments for the sensor to be on either side of the phone (or ON the side). I have a phone with the sensor on the back, and while it is inconvenient when I am doing a quick check or it is in a mount (rare), it is a more natural place when you are actually picking up the phone.