I know about send message to any number using WhatsApp official API using
https://api.whatsapp.com/send?phone=
But is there any way to sen
The WhatsApp Business API Client supports a subset of the features provided by the WhatsApp applications you already know from Android, iOS, Web and other platforms including end-to-end encryption. The difference is that this application can be deployed on a server, providing a local API that allows you to programmatically send and receive messages and integrate this workflow with your own systems (CRMs, customer care, etc.).
So in Business API its possible to send messages to the group also. You can check here. The following are the sample command for sending group message :
POST /v1/messages
{
"preview_url": false | true,
"recipient_type": "group",
"to": "whatsapp-group-id",
"render_mentions": true | false,
"type": "text",
"text": {
"body": "your-text-message-content"
}
}
Currently, this is not possible with WhatsApp. Other messenger have an open API (e.g. Facebook messenger) which allow such features. See here.