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Flock (Discontinued)

A secure contact and calendar syncing application for Android.

Flock is a replacement for the default contact and calendar synchronization services provided by Google. Flock provides end-to-end encryption between multiple Android devices putting the privacy of your contacts and calendars back under your control. To facilitate syncing between multiple devices a "sync service" is required, this can be any standards compliant WebDAV server that conforms to the following RFCs:

  1. RFC 2518 - HTTP Extensions for Distributed Authoring -- WEBDAV
  2. RFC 4918 - HTTP Extensions for Web Distributed Authoring and Versioning (WebDAV)
  3. RFC 6352 - CardDAV: vCard Extensions to Web Distributed Authoring and Versioning (WebDAV)
  4. RFC 4791 - Calendaring Extensions to WebDAV (CalDAV)

The Android app can be downloaded through Google Play or via our alternative distribution channel. Note that the certificate presented by our alternative distribution channel is signed by the same private certificate authority pinned by Flock's trust store.

Play Store Badge

Contributing bug reports

Have a bug? Please create an issue here on GitHub!

Contributing translations

Interested in helping to translate Flock? Contribute here:


Contributing code

Instructions on how to build Flock, as well as on how to setup an IDE to modify it can be found in the file.

If you're new to the Flock codebase, we recommend going through our issues and picking out a simple bug to fix in order to get yourself familiar.

For larger changes and feature ideas, we ask that you propose it on the mailing list for a high-level discussion before implementation.

This repository is set up with BitHub, so you can make money for committing to Flock. The current BitHub price for an accepted pull request is:

Current BitHub Price

Contributing Ideas

Have something you want to say about Open Whisper Systems projects or want to be part of the conversation? Get involved in the mailing list!

Contributing Funds


You can add funds to BitHub to directly help further development efforts.



For troubleshooting and questions, please visit our support center!


Looking for documentation? Check out the wiki!

Legal things

Cryptography Notice

This distribution includes cryptographic software. The country in which you currently reside may have restrictions on the import, possession, use, and/or re-export to another country, of encryption software. BEFORE using any encryption software, please check your country's laws, regulations and policies concerning the import, possession, or use, and re-export of encryption software, to see if this is permitted. See for more information.

The U.S. Government Department of Commerce, Bureau of Industry and Security (BIS), has classified this software as Export Commodity Control Number (ECCN) 5D002.C.1, which includes information security software using or performing cryptographic functions with asymmetric algorithms. The form and manner of this distribution makes it eligible for export under the License Exception ENC Technology Software Unrestricted (TSU) exception (see the BIS Export Administration Regulations, Section 740.13) for both object code and source code.


Copyright 2014 Open Whisper Systems

Licensed under the GPLv3:


Private contact and calendar sync for Android.






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