macOS Folder Pickers Fail with Android MTP — Here's Why

When developing the HiyokoMTP app, developers encountered an unexpected roadblock: macOS’s standard file dialog, NSOpenPanel, cannot detect Android devices connected through MTP. This limitation stems from a fundamental mismatch between how macOS handles file systems and how MTP operates.

After thorough testing on an eight-year-old MacBook Air, it became clear that native macOS tools are incompatible with MTP-based storage. The issue isn’t a bug but a design constraint—macOS expects storage devices to appear as mounted volumes, while MTP relies on a stateful protocol over USB without exposing a traditional file system.

Why macOS’s Native Dialogs Ignore Android Devices

macOS integrates file system operations through APIs that assume storage is mounted as a volume. However, MTP does not function this way. Instead, it uses a protocol that communicates directly with the device over USB, managing the file hierarchy internally rather than exposing it as a mountable drive.

Previously, tools like Android File Transfer attempted to bridge this gap by creating virtual mounts, but these solutions relied on kernel extensions and suffered from reliability problems. Modern MTP implementations have moved away from this approach entirely, leaving NSOpenPanel, NSSavePanel, and even Finder integration unable to recognize MTP paths.

The consequence? Developers who need to browse or select folders on an Android device via MTP must abandon native macOS APIs and build their own solutions from scratch.

Building a Custom MTP Folder Picker

If your app requires folder selection over MTP, you’ll need to implement a custom picker. Here’s a high-level breakdown of how HiyokoMTP approaches this:

Rust (Backend) – Querying MTP Devices

The Rust backend uses Tauri’s IPC system to expose a function that lists MTP directories. This function queries the connected device for the contents of a specified path and returns the results as a structured list of objects.

#[tauri::command]
fn list_mtp_dir(path: String) -> Result<Vec<MtpObject>, String> {
    // Query MTP device and return object list
}

React (Frontend) – Creating a Custom UI

On the frontend, a React component simulates a minimal Finder-like interface. Users can navigate directories by selecting folders, and the app maintains a navigation stack to support backtracking.

// On app launch
const root = await invoke("list_mtp_dir", { path: "/" });

// When a user selects a folder
const contents = await invoke("list_mtp_dir", { path: selectedPath });

// Track navigation history
const [navStack, setNavStack] = useState<string[]>(["/"]);

While the concept is straightforward, implementing this requires significantly more effort than relying on native macOS APIs. The OS typically handles file system interactions seamlessly, so developers must recreate that functionality manually.

Current Status and Future Plans

As of now, HiyokoMTP does not include a full MTP folder picker in its current release. Users must rely on manual path entry or predefined shortcuts to access MTP storage. However, the team plans to introduce a proper folder picker in a future update.

If you’re developing an MTP client and require folder selection capabilities, the architecture outlined above is the recommended path forward. There are no shortcuts—native macOS tools simply don’t support MTP natively.

The app is available as a one-time purchase with no subscription required.

Future macOS updates may introduce better MTP support, but for now, developers working with Android devices over USB must plan for custom solutions.