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.
You can avoid multiple submission in your form by enabling Unique Submission or Unique Question feature of JotForm. Enabling Unique Submission option does not allow user to submit the form using the same IP addresses or Cookies. Enabling Unique Question option does not allow user to submit the form with the same value for the field set to the option.
For more information, you can check this article: How to Set Unique Submissions on a Form.