Is https retained on relative form action URLs?

Question

Consider a page with a form that is visited via https. If the form action has a relative URL to the form page, is the https protocol retained?

Ex: you visit:

<

Answer 1

In short: Yes, the same URL scheme is used.

In detail: Relative URLs are resolved to absolute ones on the base of the current document’s URL. So if your URL is a https URL and you don’t specify the URL scheme (obviously because otherwise you would have an absolute URL), the resolved URL uses the same URL scheme as the base URL.