In January 2021, Elastic changed Elasticsearch's license from Apache 2.0 to a dual Server Side Public License (SSPL) and Elastic License. Amazon responded by forking Elasticsearch 7.10.2 into OpenSearch.
Five years later, both projects have evolved in different directions. As Elasticsearch consultants who've deployed both, here's our unbiased comparison.
TL;DR: Quick Decision Guide
| Choose Elasticsearch If... | Choose OpenSearch If... |
|---|---|
| You need the latest ML/vector search features | You need a true open-source license (Apache 2.0) |
| You're using Elastic Cloud or want premium support | You're already on AWS (OpenSearch Service) |
| You need Elastic's security features (SIEM, endpoint) | You want to avoid vendor lock-in |
| You're building an observability platform | You're building search and don't need advanced ML |
License: The Fundamental Difference
Elasticsearch: Dual-licensed under SSPL and Elastic License 2.0. Neither is OSI-approved open source. You can't offer Elasticsearch as a managed service without Elastic's permission.
OpenSearch: Apache 2.0 license. True open source. You can do whatever you want with it, including offering it as a service.
Why This Matters
For most companies building internal applications, the license difference is irrelevant. You're not selling Elasticsearch as a service.
Where it matters:
- SaaS products embedding search: If search is a core feature you're selling, consult legal counsel
- Government/enterprise procurement: Some organizations mandate OSI-approved licenses
- Open-source purists: If philosophical alignment matters to you
Feature Comparison (2026)
Both projects share the same foundation, but have diverged significantly since 2021.
Core Search Features
Both are essentially equivalent for standard search use cases:
- Full-text search with BM25 ranking
- Custom analyzers and tokenizers
- Aggregations and faceted search
- Fuzzy matching and autocomplete
- Synonyms and stemming
If you're building document search, e-commerce search, or log analytics, both work equally well.
Vector Search / AI Features
Elasticsearch: Has invested heavily in vector search and ML. ELSER (Elastic Learned Sparse EncodeR), native vector search, and tight integration with LLMs. If you're building semantic search or RAG applications, Elasticsearch is ahead.
OpenSearch: Added k-NN search and neural search plugins. Functional but not as polished. AWS is investing in this area, so expect improvements.
Verdict: Elasticsearch leads in AI/ML features. OpenSearch is catching up but about 12-18 months behind.
Security Features
Elasticsearch: Role-based access control, field-level security, audit logging. SIEM capabilities built into Elastic Security. Endpoint protection integration.
OpenSearch: Security plugin (based on Open Distro) includes RBAC, audit logging, and compliance features. Adequate for most use cases but less integrated than Elastic's security stack.
Verdict: Elasticsearch wins for security-focused use cases (SIEM, compliance). OpenSearch is sufficient for standard search applications.
Observability
Elasticsearch: Elastic APM, Elastic Agent, tight Beats integration. The ELK stack is mature and well-documented for logging and observability.
OpenSearch: OpenSearch Dashboards (Kibana fork), Data Prepper for ingestion. Growing ecosystem but less mature than ELK.
Verdict: Elasticsearch/ELK stack is more mature for observability. OpenSearch works but requires more configuration.
Performance
Real-world performance is nearly identical for most workloads. Both use the same Lucene foundation.
In our benchmarks with 1M+ document indexes:
- Query latency: Within 5% of each other
- Indexing throughput: Nearly identical
- Resource usage: Comparable memory and CPU patterns
Don't choose based on performance claims. Choose based on features, licensing, and ecosystem fit.
Managed Service Options
Elasticsearch
- Elastic Cloud: Official managed service. Best feature parity, automatic upgrades, premium support. Available on AWS, GCP, Azure.
- Self-hosted: Free for basic use. Full control but you manage everything.
OpenSearch
- Amazon OpenSearch Service: AWS-managed. Easy setup, automatic scaling, integrated with AWS ecosystem. Previously called Amazon Elasticsearch Service.
- Self-hosted: Free, open source. Full control.
Cost comparison: Elastic Cloud tends to be more expensive but offers more features. Amazon OpenSearch Service is cost-effective if you're already on AWS. Self-hosting is cheapest but requires operational expertise.
Migration Considerations
Elasticsearch to OpenSearch
Generally straightforward if you're on Elasticsearch 7.x:
- Index formats are compatible
- Query DSL is nearly identical
- Most client libraries work with both (just change the endpoint)
Watch out for:
- Elastic-specific features (ML, SIEM) won't migrate
- Some advanced security configurations need reconfiguration
- Kibana dashboards need to be recreated in OpenSearch Dashboards
OpenSearch to Elasticsearch
Also straightforward for basic use cases. Same considerations apply in reverse.
Our Recommendation
We've deployed both in production. Here's our honest take:
Choose Elasticsearch if:
- You need vector search / semantic search / RAG
- You're building a SIEM or security analytics platform
- You want Elastic Cloud's managed service and support
- You need the latest ML features
Choose OpenSearch if:
- You need Apache 2.0 licensing for legal/procurement reasons
- You're already deep in the AWS ecosystem
- You're building standard search (document search, e-commerce, logs)
- You want to avoid potential vendor lock-in
Either works if:
- You're building full-text search for an internal application
- You need log aggregation and basic analytics
- Performance is your primary concern (they're equivalent)
Need Help Deciding?
As Elasticsearch and OpenSearch consultants, we help companies make this decision based on their specific requirements. We've implemented both for legal tech, healthcare, and enterprise clients.
The technology choice matters less than the implementation. Both can deliver sub-100ms queries on millions of documents when properly configured.