This setting restricts uploaded files to specified file extensions, which is useful when you want to allow only a certain type of files to be stored in the folder and reject other types of files. Your chosen settings will also apply to all of this folder's subfolders by default, unless you override the setting. This setting's default is as a file extension (e.g. .pdf, .txt) whitelist. If you leave this setting blank, then all file extensions are allowed as uploads to this folder. If you enter one or more extensions, only files with those extensions will be allowed.

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.

Note that 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.