WARNING: The 2.x versions of Elasticsearch have passed their EOL dates. If you are running a 2.x version, we strongly advise you to upgrade.
This documentation is no longer maintained and may be removed. For the latest information, see the current Elasticsearch documentation.
Elasticsearch is an open-source search engine built on top of Apache Lucene™, a full-text search-engine library. Lucene is arguably the most advanced, high-performance, and fully featured search engine library in existence today—both open source and proprietary.
But Lucene is just a library. To leverage its power, you need to work in Java and to integrate Lucene directly with your application. Worse, you will likely require a degree in information retrieval to understand how it works. Lucene is very complex.
Elasticsearch is also written in Java and uses Lucene internally for all of its indexing and searching, but it aims to make full-text search easy by hiding the complexities of Lucene behind a simple, coherent, RESTful API.
However, Elasticsearch is much more than just Lucene and much more than “just” full-text search. It can also be described as follows:
- A distributed real-time document store where every field is indexed and searchable
- A distributed search engine with real-time analytics
- Capable of scaling to hundreds of servers and petabytes of structured and unstructured data
And it packages up all this functionality into a standalone server that your application can talk to via a simple RESTful API, using a web client from your favorite programming language, or even from the command line.
It is easy to get started with Elasticsearch. It ships with sensible defaults and hides complicated search theory away from beginners. It just works, right out of the box. With minimal understanding, you can soon become productive.
As your knowledge grows, you can leverage more of Elasticsearch’s advanced features. The entire engine is configurable and flexible. Pick and choose from the advanced features to tailor Elasticsearch to your problem domain.
You can download, use, and modify Elasticsearch free of charge. It is available under the Apache 2 license, one of the most flexible open source licenses available. The source is hosted on GitHub at github.com/elastic/elasticsearch. See Contributing to Elasticsearch if you would like to join our amazing community of contributors!
If you have any questions related to Elasticsearch, including specific features, language clients and plugins, join the conversation at discuss.elastic.co.