---
title: SKDocumentID
framework: Core Services
role: symbol
role_heading: Type Alias
platforms: [Mac Catalyst 13.0+, macOS 10.4+]
path: coreservices/skdocumentid
---

# SKDocumentID

Defines an opaque data type representing a lightweight document identifier.

## Declaration

```swift
typealias SKDocumentID = CFIndex
```

## Discussion

Discussion Use document IDs rather than document URL objects (SKDocumentRefs) whenever possible. Using document IDs results in faster searching. You can work with document IDs using a variety of Search Kit functions. See SKIndexGetMaximumDocumentID(_:), SKIndexCopyDocumentForDocumentID(_:_:), SKIndexCopyInfoForDocumentIDs(_:_:_:_:_:), SKIndexCopyDocumentRefsForDocumentIDs(_:_:_:_:), SKIndexCopyDocumentURLsForDocumentIDs(_:_:_:_:), SKIndexCopyDocumentIDArrayForTermID(_:_:), and SKIndexCopyTermIDArrayForDocumentID(_:_:).