This setting restricts files in the folder to those with the specified file extensions.

It is especially useful when you want to enforce strict file type policies, such as allowing only documents like .pdf or .txt, and blocking all others.

The restriction applies not just to file uploads, but also to any action that places a file into the folder. This includes renaming a file in a way that would result in a restricted extension, manually copying or moving files into the folder, as well as automated processes like Remote Syncs or Automations that attempt to deliver files into the folder.

If left blank, the folder will accept files of any extension.

By default, the setting behaves as a whitelist and only the extensions you specify will be accepted.

You can also toggle this setting to behave as a blacklist rather than a whitelist. Set it to blacklist mode and enter the extensions that you would like to prevent from being uploaded.

The rule also applies to all subfolders unless explicitly overridden at a deeper level.

Moving or copying folders to destination folders with filename restrictions, such as limiting uploaded files to specific file extensions, is not allowed.

Overriding Settings in Subfolders or Excluding Subfolders Entirely

You can override or exclude this setting entirely for subfolders. Users with administrator privileges can customize file extension restrictions independently of the parent folder. To exclude or override a subfolder from the parent's file extension restrictions, an admin with adequate privileges can navigate to the subfolder's settings and select the option Limit uploaded files to certain file extensions to set unique file extension rules or override the parent folder's settings.