averageradical

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:
<pre><code>[hidden referrer id:referrer]
</code></pre>
And then add to the Mail’s Message Body:
<pre><code>Referrer: [referrer]
</code></pre>
If you’re just integrating this with HTML, just add this to any form:
<pre><code><input type="hidden" id="referrer" name="referrer" />
</code></pre>

track-incoming-referrer

Track incoming referrer and write it to any hidden form field with the identifier "referrer".

storereferrals

<a href="https://www.storereferrals.com" rel="nofollow ugc">Store Referrals</a> allows you to create, manage, and track multiple campaigns with tiered rewards. This plugin will track all referred traffic and then update your dashboard analytics in real time. Also, you can optionally display a small prompt for customers to join your referral program after checkout.
<ul>
<li>Create unlimited campaigns with tiered rewards.</li>
<li>Set how many clicks and conversions are required to earn each reward.</li>
<li>Add sample social media posts for your referrers to use when promoting your store.</li>
<li>Easily recruit your customers to join to your campaigns.</li>
<li>Export lists of referrers who have qualified for rewards.</li>
<li>Get real time analytics of how many clicks, conversions, revenue, and referrer sign ups your campaigns have generated.</li>
</ul>

Store Referrals for WooCommerce

Store Referrals is a new kind of referral program that lets you spread awareness of your store using tiered rewards.

track-incoming-referrer vs Store Referrals for WooCommerce