You can run JavaScript on a URL attribute like this.

You can send an email like this.

You can initiate a call session on a smart phone like this.

You can initiate an SMS session on a smart phone like this.

You can initiate a WhatsApp session on a smart phone like this, where +44 is the country code. (For this demo to work, first click the FULL button above the code editor.

You can initiate a Skype session like this. Besides 'chat', other actions include 'add', 'call', 'sendfile', 'userinfo', and 'voicemail'.

You can download a file like this.