track-incoming-referrer

Non-technical summary: Track incoming referrer and write it to any hidden form field with the identifier « referrer » (this can be created in Contact Form 7, for example; see below). Also if the WordPress site redirects from HTTP to HTTPS, this plugin also overrides the redirect to add the referrer to the https URL.

Technical details: This plugin runs client-side JavaScript in every page in HEAD and if there isn’t a session cookie with the name « referrer », then it writes a session cookie with the name « referrer » and the value of either document.referrer, or if that’s empty, the URL-encoded value of window.location.href. There is another client-side JavaScript in every page before which writes the value of the « referrer » cookie to any INPUT with the ID « referrer », if it exists.

When integrating with Contact Form 7, add a hidden input field such as the following:

And then add to the Mail’s Message Body:

If you’re just integrating this with HTML, just add this to any form: