# ReadableDocument A document type that supports reading from file. ``` protocol ReadableDocument : AnyObject ``` ## Overview Conform to `ReadableDocument` to build a read-only document viewer, or combine with [`WritableDocument`](/documentation/SwiftUI/WritableDocument) (via the [`Document`](/documentation/SwiftUI/Document) protocol) for full read-write support. A readable document is a reference type so that SwiftUI can maintain a stable identity across updates. Use `@Observable` to enable per-property change tracking: ``` @Observable final class MarkdownViewer: ReadableDocument { static let readableContentTypes: [UTType] = [.markdown] var attributedText = AttributedString() func reader(configuration: sending ReadConfiguration) -> sending FileWrapperDocumentReader { FileWrapperDocumentReader(configuration) { fileWrapper in guard let data = fileWrapper.regularFileContents else { throw CocoaError(.fileReadCorruptFile) } return String(decoding: data, as: UTF8.self) } } @MainActor func apply(snapshot: sending String, previous: sending String?) async throws { attributedText = try AttributedString( markdown: snapshot ) } } ``` Present a read-only document with [`DocumentGroup`](/documentation/SwiftUI/DocumentGroup) using the viewer initializer: ``` DocumentGroup { document in MarkdownView(document: document) } makeReadableDocument: { configuration, context in MarkdownViewer() } ``` Set `CFBundleTypeRole` to `Viewer` in your Info.plist for read-only document types. ## Topics ### Reading a document [`readableContentTypes`](/documentation/SwiftUI/ReadableDocument/readableContentTypes) The content types this document can open. [`ReadConfiguration`](/documentation/SwiftUI/ReadableDocument/ReadConfiguration) The configuration for reading document contents. [`Reader`](/documentation/SwiftUI/ReadableDocument/Reader) A type that implements reading from disk. [`reader(configuration:)`](/documentation/SwiftUI/ReadableDocument/reader(configuration:)) Creates a reader to load this document from disk. [`apply(snapshot:previous:)`](/documentation/SwiftUI/ReadableDocument/apply(snapshot:previous:)) Applies a loaded snapshot to the document model. [`writableContentTypes`](/documentation/SwiftUI/ReadableDocument/writableContentTypes) By default, a document that supports reading also supports writing the same content types. ## Relationships ### Inherited By [`Document`](/documentation/SwiftUI/Document) --- 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)