# domainIdentifier An optional identifier that represents the domain or owner of the item. ``` var domainIdentifier: String? { get set } ``` ## Discussion Specify a domain identifier to group items together and to make it easy to delete groups of items from the index. For example, you might specify an identifier for a mailbox in an account whose indexed data you want to remove when the account is deleted. In this example, [`domainIdentifier`](/documentation/CoreSpotlight/CSSearchableItem/domainIdentifier) should be of the form `.`, where neither `` nor `` contain periods. To delete all items associated with the specified account and mailbox, you can call [`deleteSearchableItems(withDomainIdentifiers:completionHandler:)`](/documentation/CoreSpotlight/CSSearchableIndex/deleteSearchableItems(withDomainIdentifiers:completionHandler:)) with a [`domainIdentifier`](/documentation/CoreSpotlight/CSSearchableItem/domainIdentifier) of `.`. Or to delete all items associated with all mailboxes in the specified account, you can call [`deleteSearchableItems(withDomainIdentifiers:completionHandler:)`](/documentation/CoreSpotlight/CSSearchableIndex/deleteSearchableItems(withDomainIdentifiers:completionHandler:)) with a [`domainIdentifier`](/documentation/CoreSpotlight/CSSearchableItem/domainIdentifier) of ``. --- 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)