Do you know if there's a way to show a message to the user that form has not been submitted before leaving the form?

I just want to clarify if I understood your question correctly. You wanted to know if it is possible to send a form without any internet connection, right?

That is not possible since form connects to Jotform server to save and pull out data. Even if you use our license version you still need to have an internet connection as Jotform is designed for online forms.

Sorry,

I thought I was writing in the search field. Any way I was not able to find an answer.

Do you know if there's a way to show a message to the user that form has not been submitted before leaving the form?

Unfortunately, I don't think we have. A workaround would be to tell your user to wait until they see the thank you page. You can use our Free Text HTML field to put this note:

Thank you!