We are advertising a free event which people can sign up for online.
People are registering themselves more than once for the event so we are getting duplicate registrations.
If we use the back end to try to add a person to an event that they are already registered for, the system does not allow it. - That's fine.
We would like to make it so people cannot register for an event they are already registered for .
Why does the online registration allow this to happen ?
Check if 'Same email address?' checkbox is ticked in Manage Event >> Configure Event >> Online Registration.
If this checkbox is enabled, CiviCRM will allow a user to register multiple times using the same email address.
Untick 'Same email address?' checkbox to prevent people from registering for the same event more than once.
Assuming you're allowing registrations from users who aren't logged in, you might check the duplicate checking rule that you're using for the event and make sure that you're collecting enough information for the rule to match.
For example, if you don't require an email address, and your duplicate matching rule matches on email address, you'll create duplicate contacts, each with their own registration.
