A Fast Path to Filesystem Sync

Since the first Dropbox API release, developers have wanted an efficient way to stay in sync with file changes in a user’s Dropbox. The new /delta API call (beta) answers that request by returning a list of delta entries that describe changes, helping your app update its local state. This is far more efficient for tracking a whole folder hierarchy than repeatedly calling /metadata.

How it Works

The application still polls /delta periodically, but each call only returns what has changed since the cursor from the last call. This eliminates the overhead of fetching complete metadata for every directory and file on each sync cycle.

Beta Limitations

This feature is in beta to gather feedback, and the interface is likely to evolve before the final release. Do not use it in production yet. For now, it is only available for app keys with Development status and only for App Folders.

Guidelines for Beta Testing

  • /delta is trickier to use than other API methods—read the full documentation carefully before implementing.
  • Delta entries are meant for your app’s internal state. Do not expose them to end users directly. You may encounter entries out of order, e.g., an “add” entry for a file before the “add” entry for its parent folder. You may also see “delete” entries for files not present in your local state.
  • Poll intelligently with back-off. While instant notification is tempting, please maintain polling intervals no shorter than 5 minutes on average.

SDK Updates and Example Code

New versions of the Python, Ruby, and Java SDKs include a search cache example program that maintains a local cache of every file name in an App Folder via /delta. This demonstrates the intended use case and patterns for handling delta entries.

Try it out and share feedback or confusion on the forum thread.