OpenSearch vs Elasticsearch Compared: Performance, Features & Cost (2026)

A detailed 2026 comparison of Elasticsearch 9.x and OpenSearch 3.x covering licensing, governance, performance benchmarks, vector search capabilities, AI/RAG features, security, observability, and managed service pricing. Key findings: OpenSearch uses Apache 2.0 and is now governed by the Linux Foundation's OpenSearch Software Foundation; Elasticsearch offers a more integrated platform (SIEM, APM, Kibana). On vector search, OpenSearch supports Faiss and up to 16,000 dimensions vs Elasticsearch's 4,096, while Elasticsearch leads with BBQ quantization and GPU acceleration. Enterprise security features (LDAP, SAML, field-level security) are free in OpenSearch but require paid subscriptions in Elasticsearch. Amazon OpenSearch Service is typically 30-50% cheaper than Elastic Cloud. The post recommends Elasticsearch for teams already invested in the Elastic ecosystem or needing full SIEM/APM, and OpenSearch for cost-sensitive, licensing-flexible, or large-scale vector search deployments.