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.
Please be noted that there are multiple features available in JotForm to avoid spam submissions.
#1. You can add captcha fields in your form but it will only be effective if there is a automated attempt to send spam submissions. It cannot prevent, if there is a human attempt to do so. Please check the screenshot below on how to add captcha filed:
#2. 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. Please take a look at the following guide which should help you set unique submission: http://www.jotform.com/help/64-How-to-Set-Unique-Submissions-on-a-Form
You can also use our unique question feature to prevent from submitting duplicate submissions. Example: You can set one of your forms question (like cell number or email address) to be a unique question. This will not allow a user to use the same cell number or email address to submit your form. The following guide should help you: http://www.jotform.com/help/223-How-to-set-Form-Limits-Based-on-a-Unique-Question
Hope this helps.
Do get back to us if you have any questions.