How to prevent duplication of registration?

hi, can i know how to prevent the same person for duplication of registration?

Hello,
You can use the “Unique Submissions” option to prevent multiple submissions. 

1. First, go to the settings page :
2. Click the “Show More Options” button
   3. Now you can set unique submissions for your form

If you choose the “Check cookies only” option you can prevent submissions that are sent from the same browser.

If you choose “Check cookies and IP”, you could also prevent submissions from the IP address. 

For further details please check, How to set unique submissions on a form 

If you have any questions, please let us know.