Uber has required both riders and drivers to wear masks since May, and while the company says that most people have followed the rules, there have been plenty of refusals, too.

That's fine. I mean, it's a free country as we're fond of saying. However, while you're free to say no to wearing a mask under certain circumstances, places of business are also free to tell you to go elsewhere for service.

Or, in Uber's case, require you to send them a mask selfie to get a ride if you've refused to wear a mask in the past.

Passengers have had to complete a checklist before getting into an Uber over the past few months, but they have not needed to take a photo of themselves wearing a mask. So, if you've been a mask-wearing "violator" in the past, you will be asked by the app to take a selfie. According to Uber, the software can even detect whether or not the rider's mask is pulled up above his or her nose.

That software was first rolled out in May, and used to make sure Uber's drivers were complying with the mandate. If the face-detection software found a driver was not wearing a mask, they were not allowed to go online, which pretty much killed their chances to make any money from riders.

Uber's senior director of product management, Sachin Kansal:

If we do have people who are still violating the policy, we want to be able to verify them with an extra step. And if they're not wearing a mask, they will not be able to take a ride.

Here's how it works: