Apache Solr is described as 'Solr is an open source enterprise search server based on Lucene search library, with XML/HTTP and JSON APIs. Its major features include powerful full-text search, hit highlighting, faceted search, dynamic clustering, database integration, and rich document handling' and is a Search Server in the development category. There are more than 25 alternatives to Apache Solr for a variety of platforms, including Linux, Web-based, Self-Hosted, Mac and Windows apps. The best Apache Solr alternative is Algolia. It's not free, so if you're looking for a free alternative, you could try Algolia or Elasticsearch. Other great apps like Apache Solr are OpenSearch, Manticore search, Searchspring and Carrot2.