Are referring websites identifiable in posted html form?

If there is a form on one website that posts to another, will the second website know the person submitting the form came from the first?

There is no identifying information in the form and both sites use HTTPS.

<form action="https://otherwebsite.com/src" method="post" target="_top">
...
</form>

edit: If it is, what ways can it be anonymized?

Solution

Referrer Header is set by the browser in normal cases. So it can be used to identify the predecessor page; but not guaranteed.

Add following <meta> tag to your HTML page (where form exists) inside the <head> . This tells browser, not to send the referrer header. Tested in WAMP/Chrome

<meta name="referrer" content="no-referrer">