# WritableDocument A document type that supports writing to file. ``` protocol WritableDocument : AnyObject ``` ## Overview Conform to `WritableDocument` to add save and export capabilities. Most documents also conform to [`ReadableDocument`](/documentation/SwiftUI/ReadableDocument) — use the [`Document`](/documentation/SwiftUI/Document) protocol as a shorthand for both. The document saving has three steps: 1. SwiftUI calls [`snapshot(contentType:)`](/documentation/SwiftUI/WritableDocument/snapshot(contentType:)) on the main actor. 2. SwiftUI calls [`writer(configuration:)`](/documentation/SwiftUI/WritableDocument/writer(configuration:)) to get a writer. 3. The writer’s `DocumentWriter/write(content:to:previous:progress:)` runs in the background with coordinated file access. > Important: Without registered undo actions, SwiftUI won’t > trigger autosave. Register undo actions with the undo manager > from the `View` environment for every user-facing change. Example using [`FileWrapperDocumentWriter`](/documentation/SwiftUI/FileWrapperDocumentWriter): ``` @Observable final class NoteDocument: WritableDocument { static let writableContentTypes: [UTType] = [.markdown] var text = "" func writer(configuration: sending WriteConfiguration) -> sending FileWrapperDocumentWriter { FileWrapperDocumentWriter(configuration) { snapshot, _ in FileWrapper( regularFileWithContents: Data(snapshot.utf8) ) } } @MainActor func snapshot(contentType: UTType) async throws -> sending String { text } } ``` Register undo actions in the view using the environment’s `UndoManager`. This ensures SwiftUI detects unsaved changes and triggers autosave: ``` struct NoteEditorView: View { @Bindable var document: NoteDocument @Environment(\.undoManager) private var undoManager var body: some View { TextEditor(text: $document.text) .onChange(of: document.text) { oldValue, _ in undoManager?.registerUndo( withTarget: document ) { document in document.text = oldValue } } } } ``` ## Topics ### Writing a document [`writableContentTypes`](/documentation/SwiftUI/WritableDocument/writableContentTypes) The content types this document can save or export to. [`WriteConfiguration`](/documentation/SwiftUI/WritableDocument/WriteConfiguration) The configuration for writing document contents. [`Writer`](/documentation/SwiftUI/WritableDocument/Writer) A type that implements writing to disk. [`writer(configuration:)`](/documentation/SwiftUI/WritableDocument/writer(configuration:)) Creates a writer to save this document to disk. [`snapshot(contentType:)`](/documentation/SwiftUI/WritableDocument/snapshot(contentType:)) Captures the document’s current state for saving. ## 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)