Java and Android client for Flattr API

Java Flattr Client build status

flattr4j is a free open source Java library for using the Flattr API. It can be used on Android apps, but also on Java based servers, web sites and desktop applications.

flattr4j is not an official client. It is not endorsed by or affiliated with Flattr AB or Eyeo GmbH.

Important Note

Flattr is currently changing its API. Because of that, some of the flattr4j calls are failing or not delivering the expected results any more. Sadly there is no up-to-date documentation of the current API, or about their general plans for a future API.

Are you getting a "Received fatal alert: handshake failure" exception? Try the latest OpenJDK version, or use Oracle Java.


  • Lightweight and easy to use
  • Covers the entire Flattr API
  • Also runs on Android
  • JSP tag library for inserting static and javascript Flattr buttons
  • Helps through the OAuth authentication process at Flattr, no OAuth knowledge is needed
  • With Maven and Gradle support
  • Stable and mature code base, started in 2010




flattr4j is open source software. The source code is distributed under the terms of GNU General Public License Version 3, GNU Lesser General Public License Version 3, Apache License 2.0.