Mahout is an Apache Software Foundation project that creates scalable machine learning libraries. It addresses limitations of other open source machine learning libraries such as lack of community, documentation, scalability, or licensing. Mahout began in 2008 as a Lucene subproject and became a top-level Apache project in 2010. It makes machine learning algorithms scalable by implementing them to run on Apache Hadoop for processing massive datasets. Common algorithms included are recommender systems, clustering, and classification, which see real-world use in applications such as spam filtering, product recommendations, and photo tagging.