Open Source Search Engine
Search feels like a solved problem until you run it on your own data and discover that relevance is a thousand tuning decisions - ranking, stemming, synonyms, how a typo is forgiven - that a hosted search box makes for you and hides. The open source engines here put that ranking logic in your hands and run on infrastructure you control, so the results answer to your judgment about what matters rather than to a cloud vendor's defaults and per-query bill.
Elasticsearch
Distributed RESTful search and analytics engine with vector search and near real-time indexing
Meilisearch
Open-source search engine API for hybrid full-text and semantic search in apps and websites
Milvus
Cloud-native vector database for scalable ANN search, hybrid search, and real-time updates
Khoj
Self-hostable AI second brain for chat, semantic search, agents, and research across your docs and the web
Qdrant
Vector database and search engine for semantic search with payload filtering, hybrid search, and distributed deployment
SearXNG
Free internet metasearch engine that aggregates results without tracking or profiling users
Chroma
Open-source search infrastructure for AI with in-memory prototyping and optional persistence
Typesense
Typo-tolerant search engine for search-as-you-type, full-text, geo, semantic, and vector search
Sonic
Schema-less search backend that returns identifiers through a lightweight TCP protocol