Question regarding implementing two factor authentication.

I want to implement 2FA for at least one service I'm writing but I'm wondering, next to email, what services/implementations could I use?

I know that email isn't the best when it comes to security but I also don't want to force (a-technical) users to install an app specifically for 2FA so keeping email as an option as well.

But except for email, any ideas? Anything related to Google/facebook (prism integrated services) are a no go anyways (this has, as mentioned before, nothing to do with my ego or giving myself 'a pat on the back')

As for costs, I don't mind a little bit of money but the service will be free at first and I'm not rich :)

Looking forward to the comments!

😂😂😂

Source: http://knowyourmeme.com/photos/...

When i was trying to be fullstack javascript developer..*sigh*

Async/await, welcome to the family of JavaScript😀

Enabling Javascript on Windows

When will people learn that?
Java!=JavaScript

Completely agree!! 😁😁

Front end developers

Google and Siri, WTF!!