wa.me/263xxxxxxxxx?text=Hello
Opening that link will launch WhatsApp (or WhatsApp web) to the user's number and the text "Hello" in the message field.
Looks like it is some half completed demo integration rather than production ready...
Open a chat with yourself in whatsapp. https://wa.me/your-number . You can spam anything here, it's personal and only you can see it.
They send wa.me/number-of-person-you-are-contacting in that chat. Click on it and it will start a chat with person-you-are-contacting.
All numbers MUST be in international format. Country code and number.
Android v8, Firefox v68.6.
Open firefox settings, toggle 'open links in app'.
(or)
Open a chat with yourself in whatsapp. https://wa.me/your-number . You can spam anything here, it's personal and only you can see it.
They send wa.me/number-of-person-you-are-contacting in that chat. Click on it and it will start a chat with person-you-are-contacting.
All numbers MUST be in international format. Country code and number.