How to insert links to the site to Viber, Whatsapp and Telegram, when clicking on which the application opened and immediately went to the chat with the specified number. Well, and accordingly, considering mobile devices.
With Viber, it turned out like this:
<a href="viber://forward?text=Номер телефона"</a>
Viber opens, he writes an error "The action cannot be performed."
Whatsapp with Telegram open the program but are silent at all
<a href="viber://add?number=номер телефона">
phone in the format + (country code) number. + replace with% 2B