LATEST UPDATE
Now you can use the latest API from whatsapp https://wa.me/
without worrying about the user agent, the API will do the user agent handling.
Share pre-filled text with contact selection option in respective whatsapp client (Android / iOS / Webapp):
https://wa.me/?text=urlencodedtext
Open Chat Dialog for a particular whatsapp user in respective whatsapp client (Android / iOS / Webapp):
https://wa.me/whatsappphonenumber
Share pre-filled text with a particular user (Combine above two):
https://wa.me/whatsappphonenumber/?text=urlencodedtext
Note : whatsappphonenumber
should be full phone number in international format. Omit any zeroes, brackets or dashes when adding the phone number in international format.
For official documentation visit https://faq.whatsapp.com/en/general/26000030