In addition to copy-pasting(or hand-typing) the Tox ID into your client to initiate a Friend Request, Tox also supports the use of “Tox:” URI's to create hyperlinks which will launch the user's Tox client automatically and copy your Tox ID into it's “Add Friend” field(Assuming the user has configured his browser to handle Tox: links with the Tox client). qTox, Antidote, Antox, and uTox all support Tox: URI's.

Tox: links are written very similarly to regular web links, magnet links, or many other types of links you're already used to. For example, this is how you would create a link to the Tox groupbot.

<a href="tox:56A1ADE4B65B86BCD51CC73E2CD4E542179F47959FE3E0E21B4B0ACDADE51855D34D34D37CB5">Tox Groupbot</a>
 |       |   |                                                                             | Link Text.
 |       |   | Target Tox ID
 |       | Tox URI scheme(Note, no //)
 | Open <a> tag

That's it.