OpenSearch vs Elasticsearch: How the Fork Has Diverged

Elasticsearch and Kibana were Apache 2.0 until Elastic moved their source to dual licensing under the Server Side Public License (SSPL) and the Elastic License, shortly before the 7.11 release in early 2021. Elastic has said the change was aimed at cloud providers, AWS in particular, offering Elasticsearch as a service. AWS responded on 12 April 2021 with the OpenSearch project: OpenSearch derived from Elasticsearch 7.10.2 and OpenSearch Dashboards from Kibana 7.10.2, both Apache 2.0, with the features of its earlier Open Distro for Elasticsearch folded in. OpenSearch 1.0 followed in July 2021, and Amazon Elasticsearch Service was renamed Amazon OpenSearch Service.

Two later events reshaped the picture. On 29 August 2024 Elastic announced that it would add the OSI-approved AGPLv3 as a third license option, which took effect before Elasticsearch 8.16 became generally available. Elastic's licensing FAQ is precise about the scope: AGPLv3 applies to the free portions of the source code, while Elastic's binary releases continue under the Elastic License. Then on 16 September 2024 AWS transferred OpenSearch to the newly launched OpenSearch Software Foundation, hosted by the Linux Foundation, with AWS, SAP and Uber as premier members.

Yes, to download and run. The default Elasticsearch distribution is free under the Elastic License 2.0, which allows internal use but prohibits offering Elasticsearch to others as a managed service. The free Basic tier includes TLS, users and role-based access control, and Kibana. Machine learning, field- and document-level security, cross-cluster replication and several other features require a paid subscription, as does Elastic support. If you need an OSI-approved license for the code itself, AGPLv3 now covers the free portions of the source; AGPL obligations apply if you modify it and offer it over a network. OpenSearch is free under Apache 2.0 with no feature tiers, and commercial support comes from AWS, hosted providers or independent firms.

Security. OpenSearch ships its Security plugin in the open-source distribution: TLS, authentication backends, roles, field- and document-level security and audit logging. Elasticsearch made TLS and role-based access control free in 6.8 and 7.1 and turns security on by default from 8.0, but keeps finer-grained controls on paid tiers.

Query languages. Both still speak the JSON Query DSL, so most search and aggregation queries look alike. Elastic added ES|QL, a piped query language that became generally available in 8.14, alongside EQL and SQL. OpenSearch offers SQL and PPL, its own piped language, through its SQL plugin. Saved queries in one do not run in the other.

Vector search. Both store vectors and run approximate k-NN search with HNSW. OpenSearch's k-NN plugin offers the Lucene and Faiss engines, with Faiss adding IVF and further compression options; the older NMSLIB engine is deprecated. Elasticsearch uses dense_vector and sparse_vector fields on Lucene with quantization, and semantic_text to handle embedding at ingest.

Dashboards and solutions. Kibana and OpenSearch Dashboards look similar for basic visualization but have diverged in plugins and observability and security tooling. Elastic packages Kibana into its Observability and Security solutions; OpenSearch provides observability, security analytics and anomaly detection plugins.

OpenSearch kept the REST API and index format of Elasticsearch 7.10.2, so applications written against 7.10 or earlier usually need only client and endpoint changes. Clients are the first thing to check: Elastic's official clients from 7.14 verify that the server identifies itself as Elasticsearch and refuse to connect otherwise, so OpenSearch applications use the OpenSearch client libraries. Beyond 7.10 the two have diverged in mappings, APIs and plugins, so data from a later Elasticsearch 7.x, 8.x or 9.x cluster normally moves by reindexing rather than snapshot restore. AWS publishes a Migration Assistant for Amazon OpenSearch Service for these moves. Going the other way, from OpenSearch to Elasticsearch, is also a reindex plus a rewrite of anything using PPL, security plugin APIs or k-NN mappings.

Amazon OpenSearch Service runs OpenSearch and legacy Elasticsearch OSS up to 7.10, plus a serverless option. AWS charges Extended Support on versions past standard support: Elasticsearch 7.10 reaches end of standard support on 7 November 2027 and end of extended support on 7 November 2030. Elastic Cloud is Elastic's own service on AWS, Google Cloud and Azure, with hosted and serverless deployments, and the service that tracks new Elasticsearch releases with Elastic's full feature set. Several other providers host OpenSearch. Self-managed remains common on both sides, especially where data residency rules out a hosted service.

Elastic maintains a major line for 30 months from its release or 18 months after the next major, whichever is later, plus six months of support. Elasticsearch 7.17 reached end of maintenance on 15 April 2025 and end of support on 15 January 2026. 8.x ends maintenance on 15 January 2027 and support on 15 July 2027. 9.x is maintained until at least 15 October 2027. OpenSearch maintains the current major and keeps the previous one in maintenance until the next major enters maintenance or for at least a year: OpenSearch 1.x reached end of life on 6 May 2025, 2.x is in maintenance until 4.0 ships, and 3.x is current.

Teams pinned to Elasticsearch 7.x, often because 7.10.2 is the last Apache 2.0 release or because 8.x needs a reindex, now run without upstream fixes. AceMQ's OSSeva service provides patched builds of self-managed Elasticsearch 7.10.2 and 7.17 while the move to 8.x, 9.x or OpenSearch is planned. Full dates are in Elasticsearch end of life dates and support options.

1. Do you need Apache 2.0 terms, or will you offer search as a service to others? OpenSearch.
2. Are you all-in on AWS and want a managed service on your AWS bill? OpenSearch, on Amazon OpenSearch Service.
3. Do you need field- and document-level security without a subscription? OpenSearch.
4. Do you rely on ES|QL, Kibana's Observability or Security solutions, or Elastic's machine learning? Elasticsearch.
5. Are you on 7.10 or 7.17 today? Either is a migration, so decide on license and features, not on which path looks shorter.