>I'm wondering if more instructions on the QR code or the page for the doorbell would work better?

In general you should display a prompt explaining why a permission is needed (eg. "we need access to your camera to camera to take a picture to send to the owner, click allow on the next screen to allow."), and only ask for permissions after the user accepts the first prompt.

However in this particular case you shouldn't have to request camera access directly. Using <input type="file" accept="image/*" capture="user> will display an system interface (ie. from the browser or OS) to allow the user to take/select an existing picture. It also already has preview and front/back camera selector built in, so you don't have to implement that yourself.

https://developer.mozilla.org/en-US/docs/Web/HTML/Attributes...

If you're at the point of asking permissions, might as well grab the location data as well. You could then verify that the person hitting the QR code is actually on your front step which would eliminate all of the false positives like the replay attacks, copies being used in other locations, etc.

100% agree with explaining before asking permission.

I'll have a look at using the `capture` attribute on an input. My initial idea was to do video over webRTC, but the selfie version works okay for a first version

There are tons of cheap wireless units available that just use a bit of sticky tape to "install" the button to the door and then you can place the receiver/bell where ever you want. These work well and are much more understood by visitors.

Of course, you would not have learned your first iOS/Android app with that approach. Maybe that's the better lesson to learn though--not everything needs to be an app

So while I find that idea interesting, I would rather prefer knocking or texting on the doorstep of peoples homes.

I might have a situation where the QR Code makes sense though. I'm renting a location for a party at the top of a building, which is only accessible by transponder cards. So there is no door bell or anything. Instead of having someone letting the guests in, this could be an alternative.