JotForm is a free online form builder which helps you create online forms without writing a single line of code. No sign-up required.
We believe that if one user has a question, there could be more users who may have the same question. This is why many of our support forum threads are public and available to be searched and viewed. If you’d like help immediately, feel free to search for a similar question, or submit your question or concern.
Generally, when the form is embedded on your webpage it displays the thank you message on the same page as on your website. So, the users shall not be leaving your website once the form is submitted unless your thank you message is redirected to another URL.
You may also try other embedding options to display the form on a different tab or lightbox popup.
Hope this information helps. Let us know if you have any other questions.