Wherever possible, forms run over HTTPS. However, depending on how the form has been shared, this may not be possible.
The situations in which forms won't run over HTTPS are when:
- The page or form is embedded in a site that isn't running over HTTPS
- The page or form is running as a pop-over on a site that's not running over HTTPS
You don't need to do anything to a form to make it run in the right mode - it's automatic.