# Elasticsearch vs OpenSearch

> OpenSearch and Elasticsearch score within a point of each other for vector search, 68 and 67.7 out of 100. Prices, MCP, x402, uptime and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/elasticsearch-vs-opensearch
- Markdown: https://www.anchorterminal.com/compare/elasticsearch-vs-opensearch.md (~2,600 tokens)
- Slim: https://www.anchorterminal.com/compare/elasticsearch-vs-opensearch.min.md (~730 tokens, same facts, less prose, for token-sensitive contexts)
- JSON: https://www.anchorterminal.com/compare/elasticsearch-vs-opensearch.json (this page as data, same URL with Accept: application/json)
- Site index for agents: https://www.anchorterminal.com/llms.txt (full text: https://www.anchorterminal.com/llms-full.txt)
- API: https://www.anchorterminal.com/api/v1/index.json
- Updated: 2026-10-09

OpenSearch and Elasticsearch score within a point of each other on agent readiness, 68 (B) and 67.7 (B). Elasticsearch leads on schema & documentation and transparency & trust. Both do vector search.

- Elasticsearch: grade B, 67.7/100, rank #242 of 950. Markdown https://www.anchorterminal.com/tools/elasticsearch.md · JSON https://www.anchorterminal.com/api/v1/tools/elasticsearch.json
- OpenSearch: grade B, 68/100, rank #233 of 950. Markdown https://www.anchorterminal.com/tools/opensearch.md · JSON https://www.anchorterminal.com/api/v1/tools/opensearch.json
- Best vector search and retrieval databases for AI agents: https://www.anchorterminal.com/best/vector-search/index.md
- All 85 retrieval comparisons: https://www.anchorterminal.com/compare/vector-search/index.md

## Which one, for what

### Elasticsearch (B)

Good for: Retrieval that needs keyword relevance, filters and vectors in one query, and teams already running Elastic for logs or security.

Ahead on:
- Schema & documentation, 88 against 77
- Transparency & trust, 71 against 57

Also in its favour:
- Free to start without a card

Watch for: More than 20 status notices marked major between 10 July and 8 October 2026, three of them regional service incidents

### OpenSearch (B)

Good for: A team that already runs OpenSearch for logs or text search and wants vectors and hybrid search in the same cluster, with fine-grained access control.

Ahead on:
- Reliability, 77 against 62
- Payments & pricing, 60 against 35

Also in its favour:
- Runs on your own machine

Watch for: No hosted service from the foundation. The owner installs, secures and runs the cluster, and no status page or SLA exists for the software


## Score by category

| Category | Weight | Elasticsearch | OpenSearch | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 62 | 77 | OpenSearch +15 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 88 | 77 | Elasticsearch +11 |
| Agent ergonomics | 13% (16.2 this run) | 77 | 80 | OpenSearch +3 |
| Security & auth | 14% (17.5 this run) | 72 | 70 | Elasticsearch +2 |
| Payments & pricing | 10% (12.5 this run) | 35 | 60 | OpenSearch +25 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 83 | 84 | OpenSearch +1 |
| Transparency & trust | 7% (8.8 this run) | 71 | 57 | Elasticsearch +14 |
| Negative events | ≤15 | -2 | -5 | |
| **Total** | | **67.7 · B** | **68 · B** | |

## Facts side by side

| Fact | Elasticsearch | OpenSearch |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | Elastic | OpenSearch Software Foundation |
| Hosted endpoint | no (local only) | no (local only) |
| Transports | HTTP | HTTP, stdio |
| Auth | OAuth or key | OAuth or key |
| Pricing | Pay per use | Free |
| x402 | no | no |
| Licence | AGPL-3.0, SSPL-1.0 or Elastic Licence 2.0 at the user's choice for most source. The `x-pack` folder is under Elastic Licence 2.0 only. Elastic Cloud is a proprietary service under Elastic's terms | Apache-2.0 for the engine, the plugins, the clients, the API specification and the MCP server |
| Tools exposed | none | 9 |
| Read-only variant documented | no | no |
| llms.txt | yes | no |
| Last release | 2026-10-06 | 2026-09-22 |
| Terms last updated | couldn't be read | no document linked |
| Privacy policy last updated | 2026-09-07 | no document linked |
| Customer content may train models | couldn't be read |  |
| Terms restrict automated access | couldn't be read |  |
| Terms restrict benchmarking | couldn't be read |  |
| Terms or service can change without notice | couldn't be read |  |
| Arbitration or class-action waiver | couldn't be read |  |
| Popularity | 3.1M npm/wk, 7.8M PyPI/wk | 14k stars |

## Verdicts

**Elasticsearch.** Keyword, dense and sparse vector, and hybrid search with rank fusion sit behind one OpenAPI-described REST API, with API keys scoped to indices and privileges. The status page lists more than 20 incidents marked major since July 2026, and Elasticsearch 9.5.0 returned incorrect results for some queries without raising an error.

**OpenSearch.** OpenSearch 3.9.0 runs vector, text and hybrid search under Apache-2.0, with an OpenAPI 3.1 description of its REST API and API keys limited by permission and index pattern. The owner runs the cluster, no status page or SLA comes with the software, and no tool in the MCP server sets a read-only or destructive annotation.

## Before you call either

### Elasticsearch

1. Send `Authorization: ApiKey <key>` to the project's Elasticsearch URL. The MCP server is on the Kibana URL at `/api/agent_builder/mcp`
2. Create the MCP key with `feature_agentBuilder.read` and only the index patterns needed, or the endpoint answers 403
3. On 429, wait and retry with exponential backoff. Do not set short client timeouts, because a retried request joins the back of the queue
4. Page past 10,000 hits with `search_after`, not `from` and `size`
5. Tool calls made directly through the Tools API skip Agent Builder's confirmation prompts, so restrict the key instead

### OpenSearch

1. Create the index with `index.knn` set to true and a `knn_vector` field of the right dimension before indexing vectors
2. Put the `filter` clause inside the `knn` query for filtering during the search. A filter outside it runs afterwards and can return fewer than `k` hits
3. Ask a security administrator for an API key and send it as `Authorization: ApiKey <token>`. The token is shown once and lasts 90 days at most
4. Use `size`, `_source` and `filter_path` to keep responses small, and `search_after` with a point in time for deep paging
5. Set `OPENSEARCH_SETTINGS_ALLOW_WRITE=false` on the MCP server unless writes are needed. `GenericOpenSearchApiTool` can call any endpoint

## Questions

### Which is better for AI agents, Elasticsearch or OpenSearch?

OpenSearch and Elasticsearch score within a point of each other on agent readiness, 68 (B) and 67.7 (B). Elasticsearch leads on schema & documentation and transparency & trust.

### Do Elasticsearch and OpenSearch need an API key?

Both take an API key or an OAuth sign-in.

### Can an agent call Elasticsearch and OpenSearch without installing anything?

No hosted endpoint is listed for Elasticsearch. OpenSearch runs on your own machine, with no hosted endpoint listed.

### Are Elasticsearch and OpenSearch open source?

Yes. Elasticsearch is open source (AGPL-3.0, SSPL-1.0 or Elastic Licence 2.0 at the user's choice for most source. The `x-pack` folder is under Elastic Licence 2.0 only. Elastic Cloud is a proprietary service under Elastic's terms). OpenSearch is open source (Apache-2.0 for the engine, the plugins, the clients, the API specification and the MCP server).


## For agents

- This comparison as JSON: https://www.anchorterminal.com/compare/elasticsearch-vs-opensearch.json, and with the fewest tokens: https://www.anchorterminal.com/compare/elasticsearch-vs-opensearch.min.md
- Over MCP at https://www.anchorterminal.com/mcp (no key): `compare_tools {"a": "elasticsearch", "b": "opensearch"}`. From a terminal: `anchor compare elasticsearch opensearch`
- Each listing in full: https://www.anchorterminal.com/api/v1/tools/elasticsearch.json and https://www.anchorterminal.com/api/v1/tools/opensearch.json

## Other comparisons with Elasticsearch or OpenSearch

- [Chroma API + MCP vs Elasticsearch](https://www.anchorterminal.com/compare/chroma-vs-elasticsearch.md)
- [Chroma API + MCP vs OpenSearch](https://www.anchorterminal.com/compare/chroma-vs-opensearch.md)
- [Elasticsearch vs Epsilla Vector Database](https://www.anchorterminal.com/compare/elasticsearch-vs-epsilla.md)
- [Elasticsearch vs LanceDB](https://www.anchorterminal.com/compare/elasticsearch-vs-lancedb.md)
- [Elasticsearch vs Meilisearch](https://www.anchorterminal.com/compare/elasticsearch-vs-meilisearch.md)
- [Elasticsearch vs Milvus and Zilliz Cloud API + MCP](https://www.anchorterminal.com/compare/elasticsearch-vs-milvus-zilliz.md)
- [Elasticsearch vs Pinecone API + MCP](https://www.anchorterminal.com/compare/elasticsearch-vs-pinecone.md)
- [Elasticsearch vs Qdrant API + MCP](https://www.anchorterminal.com/compare/elasticsearch-vs-qdrant.md)
- [Elasticsearch vs Typesense API + MCP](https://www.anchorterminal.com/compare/elasticsearch-vs-typesense.md)
- [Elasticsearch vs Upstash Vector API + MCP](https://www.anchorterminal.com/compare/elasticsearch-vs-upstash-vector.md)
- [Elasticsearch vs Vespa](https://www.anchorterminal.com/compare/elasticsearch-vs-vespa.md)
- [Elasticsearch vs Weaviate API + MCP](https://www.anchorterminal.com/compare/elasticsearch-vs-weaviate.md)
- [Epsilla Vector Database vs OpenSearch](https://www.anchorterminal.com/compare/epsilla-vs-opensearch.md)
- [LanceDB vs OpenSearch](https://www.anchorterminal.com/compare/lancedb-vs-opensearch.md)
- [Meilisearch vs OpenSearch](https://www.anchorterminal.com/compare/meilisearch-vs-opensearch.md)
- [Milvus and Zilliz Cloud API + MCP vs OpenSearch](https://www.anchorterminal.com/compare/milvus-zilliz-vs-opensearch.md)
- [OpenSearch vs Pinecone API + MCP](https://www.anchorterminal.com/compare/opensearch-vs-pinecone.md)
- [OpenSearch vs Qdrant API + MCP](https://www.anchorterminal.com/compare/opensearch-vs-qdrant.md)
- [OpenSearch vs Typesense API + MCP](https://www.anchorterminal.com/compare/opensearch-vs-typesense.md)
- [OpenSearch vs Upstash Vector API + MCP](https://www.anchorterminal.com/compare/opensearch-vs-upstash-vector.md)
- [OpenSearch vs Vespa](https://www.anchorterminal.com/compare/opensearch-vs-vespa.md)
- [OpenSearch vs Weaviate API + MCP](https://www.anchorterminal.com/compare/opensearch-vs-weaviate.md)