Are you trying to prevent duplicate records from being entered into your system?
If so, there is no built-in or automated way to do that, either from a form or from the built-in native Airtable tools.
You’d have to automate your own procedure after the form is submitted to look for duplicate values, or use the grouping feature to manually scan for duplicates, or manually use the Dedupe app to scan for duplicates.
However, this extension was created to stop duplicate values from being submitted through a form:
