Authorization for public web forms

After saving a form, go to Settings → Sharing where you can find Access management.

First setting available is a toggle Allow only authenticated users (Microsoft Account):

Allow only authenticated users (Microsoft Account)

Once you turn it on - users will need to be authorized. New settings will become available to choose from.

You can restrict submissions to just one per user. If you do - you can also allow users to go back to form and edit their submission (each edit counts as a submission and will trigger a flow/zap again):

Allow users to submit the form just once

Finally, you can restrict access to specific users by enabling Restrict access to specific users or groups (Azure AD) and inputting a Microsoft 365 domain:

Restrict access to a domain

This will require you to authorize the app to access domain and retrieve information about the users:

Grant permissions to the permissions

On top of that, you will also be able to select specific Azure Active Directory groups or even individual users to provide access to:

Limit access to specific users/Azure AD groups

Users without permissions will not be able to access the form:

No access to the form