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.
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Inside of this guide you can find out how to set Form Limits Based on a Unique Question:
You can take advantage of our unique submission feature to block multiple submissions from one system of one IP address by setting the "Loose check" or "Strict Check" respectively. Here is a guide to help you set unique submission in your form: http://www.jotform.com/help/64-How-to-Set-Unique-Submissions-on-a-Form
Hope this will help. Let us know if you need further assistance.