# localizedReferenceDocumentation(forFilterName:) Returns the location of the localized reference documentation that describes the filter. ``` class func localizedReferenceDocumentation(forFilterName filterName: String) -> URL? ``` ## Parameters `filterName` The filter name. ## Return Value A URL that specifies the location of the localized documentation, or `nil` if the filter does not provide localized reference documentation. ## Discussion The URL can be a local file or a remote document on a web server. Because filters created prior to OS X v10.5 could return `nil`, you should be make sure that your code handles this case gracefully. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)