Lucene is a Java-based search library available for free as open source under the liberal Apache Software License. This license allows users to modify or embed the technology as they see fit, and to keep proprietary, sell and/or re-distribute any resulting product. Lucene is written entirely in Java, though there are today .NET and other versions available. Lucene has a large number of active contributors and thousands of installations, including production applications at AOL, Apple, CNET, Comcast Interactive Media, IBM, LinkedIn, Monster, MySpace, Netflix, Technorati and Wikipedia. Lucene is full-featured and provides:

• Speed — sub-second query performance for most queries
• Strong out of the box relevancy ranking — as good or better than the best commercial competitors
• Complete query capabilities: keyword, Boolean and +/- queries,proximity operators, wildcards, fielded searching, term/field/document weights, find-similar, spell-checking, multi-lingual search and more
• Full results processing, including sorting by relevancy, date or any field, dynamic summaries and hit highlighting
• Portability: runs on any platform supporting Java, and indexes are portable across platforms - you can build an index on Linux and copy it to a Microsoft Windows machine and search it there
• Scalability — there are production applications in the hundreds of millions and billions of documents/records
• Low overhead indexes and rapid incremental indexing, especially with versions 2.3 and later

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