Prepare the storage
- Connect the external drive to iPhone, or make sure the compatible Files provider is available in the Files app.
- Choose a writable folder with enough free space.
- Do not use a network share or cloud drive mounted elsewhere as External Storage. Use the dedicated SMB, WebDAV, SFTP, S3-Compatible, or OneDrive Node type instead.
- If the drive cannot be written to, check its format first. Apple's external storage guidance for iPhone is a useful reference.
Add the Node
- In Watermelon Backup, choose Add External Storage.
- Use the iOS Files picker to select the backup folder.
- Give the Node a name if needed; otherwise the folder name is used.
- Save the Node and select it on Home.
- Keep the drive or Files provider available while the task runs.
Run the backup
- Wait for the Node to connect and for the remote index to finish syncing.
- Grant Photos access if needed.
- Check the local-side months you want to back up.
- Tap Execute and confirm the task.
- After completion, keep the storage available until Watermelon Backup finishes writing the month manifest.
Limits
- Background Auto-Backup does not support External Storage.
- iOS controls security-scoped access to the selected folder; reconnect or reselect the folder if access is lost.
Download Watermelon Backup
Install Watermelon Backup from the App Store to follow this guide on iPhone.