When you begin your business using Twillio for sms verification is pretty expensive, I was looking for a free/very cheap service for the beginning.
I can see that Facebook provides - Whatsapp business API and it's unclear if you can already use it to send messages as an individual developer.
https://developers.facebook.com/docs/whatsapp/
I can see that Twillio also have a Whatsapp API which costs money.
Is there a way to send Whatsapp messages today ?
Is there other affordable choice to verify new users by sms ?
There are few Whatsapp non officials API like for example this one or this one. I'm actually also interested in using Whatsapp for sending authentication codes so I'm "collecting" the links for the moment without testing so far. Be careful: it's said quite often that Whatapp is very smart at detecting and blacklisting non regugar usage...
I was also looking at more industrial solutions with Google's firebase or Facebook's account kit. They might be a good alternative yet the pricing model is not crystal clear for me.