To create your own link with a pre-filled message that will automatically appear in the text field of a chat, use https://wa.me/whatsappphonenumber/?text=urlencodedtext
where whatsappphonenumber is a full phone number in international format and URL-encodedtext is the URL-encoded pre-filled message.
Example:https://wa.me/15551234567?text=I'm%20interested%20in%20your%20car%20for%20sale
https://faq.whatsapp.com/en/android/26000030/
or
<a href="https://api.whatsapp.com/send?phone=0123456789&text=I'm%20interested%20in%20your%20services" target="_blank"> Click to WhatsApp Chat</a>
The message in the url shows in the input field of whatsapp message box is there a way so that the message gets posted or sent automatically ? Reason behind it- There will be a icon on the website for whatsap chat anyone who clicks on that icon his message should be automatically send to the website's contact number which is in the url.