On the meta platforms I am intricately familiar with the Whatsapp API and it is literally not possible unless you are effectively going to effectively run WhatsApp Web in a browser instance and interact with it which is against ToS.
Whatsapp API works on the basis of conversations, the conversation has to be initiated by another party and only exists for 24hours from the last message from the other party. Sending messages unprompted is not possible unless it’s a templated message.
I can believe this exists to counter spam, and let’s not ignore the fact that WhatsApp messages through the API costs more per message than SMS.
In my experience restrictive and developer hostile API structures are indicative of exploiting a monopoly position rather than some provided excuse like 'countering spam'
WhatsApp is far from a monopoly and I wouldn’t call their api developer hostile, it’s actually reasonable to work with, what you can do with it though is quite restricted to what a business would want to do with WhatsApp and is billed accordingly.
A MASSIVE part of the world would like to disagree.
Whatsapp is to the rest of the world what iMessage is to Americans.
I'm in the reat of the world. Trust me I understand how entrenched WhatsApp is but realistically point to the viable alternative.
And WhatsApp for "the rest of the world" is "free", about as free as Gmail and Facebook but monetarily free. It's hard to argue a monopoly when there is no money trading hands, and for business you are free to contact your customers via Email or SMS or whatever other form you would like, I can tell you there is benefits to using WhatsApp, our stats show much higher engagement and well we can actually get more information about message delivery than other platforms, you pay a premium for that and they gatekeep that because it has business benefit to do so.
If WhatsApp campaigns didn't get higher engagement than email or sms which is cheaper we wouldn't pay the premium for it, everyone who has WhatsApp can also receive SMS.
Does that help clarify why I'm arguing WhatsApp isn't a monopoly? It's kind of ranty, I apologise for that.