Leadin works with most of the major WordPress form plugins and custom built HTML forms as well.
The only exceptions are forms that are not enclosed in a HTML <form> tag or if the form is loaded through an iFrame. If the form submits through Javascript we can’t detect that it’s a form, or if it’s an iFrame we can’t detect the submission because of cross site security reasons.
Here’s a list of form builders that we’ve tested so far and found to be working or not working:
Tested + supported:
Contact Form 7
JetPack
Fast Secure Contact Form
Contact Form
Gravity Forms
Formidable
Ninja Forms
Contact Form Clean and Simple
HubSpot
Native WordPress comment forms
Most custom forms
Tested + unsupported:
Wufoo
Easy Contact Forms
Disqus comments
SumoMe
Forms contained in an iFrame
Hope this answer your question and please let me know if there’s anything else I can help with.