Apache LuceneTM is a high-performance, full-featured text search engine library written entirely in Java. It is a technology suitable for nearly any application that requires full-text search, especially cross-platform. Apache Lucene is an open source project available for free download. Please use the links on the right to access Lucene. Lucene offers powerful features through a simple API: Scalable, High-Performance Indexing over 150GB/hour on modern hardware small RAM requirements -- only 1MB heap incremental indexing as fast as batch indexing index size roughly 20-30% the size of text indexed Powerful, Accurate and Efficient Search Algorithms ranked searching -- best results returned first many powerful query types: phrase queries, wildcard queries, proximity queries, range queries and more fielded searching (e.g. title, author, contents) sorting by any field multiple-index searching with merged results allows simultaneous update and searching flexible faceting, highlighting, joins and result grouping fast, memory-efficient and typo-tolerant suggesters pluggable ranking models, including the Vector Space Model and Okapi BM25 configurable storage engine (codecs) Cross-Platform Solution Available as Open Source software under the Apache License which lets you use Lucene in both commercial and Open Source programs 100%-pure Java Implementations in other programming languages available that are index-compatible