--- title: Customizing the document browser framework: uikit role: article role_heading: Article path: uikit/customizing-the-browser --- # Customizing the document browser Customize the document browser’s look and behavior. ## Overview Overview You can set the browser’s appearance, create document thumbnails, and modify the browser’s behavior. Set the browser’s appearance Change the browser’s appearance by setting the browserUserInterfaceStyle property. The document browser view controller supports white, light, and dark appearances. Create document thumbnails or icons The system automatically provides thumbnails or icons for supported document types. If your app uses a custom or third-party document type, you can create a Thumbnail extension for that type. For more information, see QLThumbnailProvider. If you don’t provide a Thumbnail extension, the system can create a document icon based on your app icon. To enable automatic icon creation, go to the Project navigator, choose the target, click Info, and then do the following: Declare support for the document’s Uniform Type Identifier in the Document Type section. For any custom document types that you create, export the Uniform Type Identifier in the Exported Type Identifiers section. For any third-party document types used by your app, import the Uniform Type Identifier in the Imported Type Identifiers section. For more information, see Set the supported document types. Your app’s icon only appears in the Files app or document browser when all of the following are true: The system doesn’t automatically provide a thumbnail for the Uniform Type Identifier. The system doesn’t already provide an icon for the Uniform Type Identifier. The user hasn’t installed a Thumbnail extension for the Uniform Type Identifier. Your app both declares document type support for the Uniform Type Identifier and declares it as an exported or imported type. Add document previews The system automatically provides previews for supported document types. If your app uses a custom or third-party document type, you can create a Preview extension for that type. For more information, see Quick Look. Modify the browser’s behavior You can control the following behaviors: The type of documents the browser opens Whether the browser opens multiple files at the same time Whether the browser creates new documents Set allowed document types You set the list of allowed document types when you create the browser. Pass an array of Uniform Type Identifier strings to the UIDocumentBrowserViewController class’s init(forOpeningFilesWithContentTypes:) method. If you pass nil, the browser uses the document types specified by the CFBundleDocumentTypes key in the app’s Info.plist file. For detailed instructions on setting the CFBundleDocumentTypes key, see Set the supported document types. The following example programmatically creates a document browser for .txt files: let browser = UIDocumentBrowserViewController(forOpeningFilesWithContentTypes: ["public.plain-text"]) Enable multiple document selection By default, users can select only one item at a time. To enable multiple document selection, set the document browser’s allowsPickingMultipleItems property to true. Enable new document creation To let users create new documents, you must do the following: Set the browser’s allowsDocumentCreation property to true (the default value). Implement the UIDocumentBrowserViewControllerDelegate object’s documentBrowser(_:didRequestDocumentCreationWithHandler:) method. After these steps are completed, the system automatically includes an Add button (+) in the document browser’s navigation bar. When the user taps the Add button, the system calls the documentBrowser(_:didRequestDocumentCreationWithHandler:) method. In your implementation, you can present a custom user interface, where users can configure the document. For example, you might show a list of document templates. Create a new document and save it to a temporary location. As soon as the document is saved, call the provided importHandler. To confirm the request, pass in the document’s temporary URL and the import mode (UIDocumentBrowserViewController.ImportMode.copy or UIDocumentBrowserViewController.ImportMode.move). To cancel the request, pass nil and UIDocumentBrowserViewController.ImportMode.none. important: You must always call the importHandler. If you can’t create a new document, pass nil for the URL and UIDocumentBrowserViewController.ImportMode.none for the import mode. ## See Also ### Customization - [Adding custom actions and activities](uikit/adding-custom-actions-and-activities.md)