UTM parameters! They're useful, and we keep making them more useful.
Now, you can supply them even in slightly unconventional ways, like in the form body itself:
<form action="https://buttondown.com/api/emails/embed-subscribe/{{ newsletter.username }}" method="post">
<input type="hidden" name="utm_source" value="website">
<input type="hidden" name="utm_campaign" value="spring2025">
<input type="hidden" name="utm_medium" value="email">
<input type="email" name="email" placeholder="Your email address">
<button type="submit">Subscribe</button>
Or in the query string to the embedded form:
https://buttondown.com/api/emails/embed-subscribe/{{ newsletter.username }}?utm_source=website&utm_campaign=spring2025&utm_medium=email
Both will be honored, with the former taking precedence.
We hope you find this useful!