It'd be possible, I think. You'd need to run WhatsApp web, which is an Electron app. Get into the dev tools and set it up directly from the JS console.

That's a nice idea if it works, bit hacky but still. I never used WA Web, will have a look.

Facebook has an API for whatsapp, which I believe is a closed beta. In theory you could build an app to do this for you, twilio supports this and let's you use a development key even before you get into the beta.

[I expect that's too many hoops for your use case though ;]

Thx! I found the Business API which is really for partners ( and for SMB's there is the Business app).

https://www.whatsapp.com/business/api

The Twilio API is in beta, and you can sign up. Don't know what pricing will be, but maybe for individual use a dev subscription may be sufficient

https://www.twilio.com/whatsapp

Here is the API reference:

https://www.twilio.com/docs/sms/whatsapp/api

Also see: https://www.messagebird.com/en/

Though, getting your own business-API would be cheaper, I've heard WhatsApp is very picky about granting those and instead prefer you work with a third-party partner instead [0].

Then, there's click-to-chat for simpler communication if the client's WA number is known [1].

[0] https://faq.whatsapp.com/en/general/26000239/?category=52452...

[1] https://faq.whatsapp.com/en/general/26000030/?category=52452...

Could you not just set you status in WhatsApp to all people to contact you via Signal?

Not as good as an auto responder but at least people would see it when searching for you in the app