Massive Online Analysis (MOA) is a free open-source software project specific for data stream mining with concept drift.

It is written in Java and developed at the University of Waikato, New Zealand.

It includes a set of learners and stream generators that can be used from the graphical user interface (GUI), the command-line, and the Java API.

MOA contains several collections of machine learning algorithms: These algorithms are designed for large scale machine learning, dealing with concept drift, and big data streams in real time.

MOA is free software released under the GNU GPL.