USearch

USearch packs an approximate nearest neighbor engine into a single C++11 header, trading the bulk of FAISS (roughly 3 thousand lines of code against 84 thousand) for portability without giving up speed. Built on the HNSW algorithm, it searches and clusters vectors with user-defined distance metrics, supports precision from 64-bit floats down through bf16, f16, i8, and single-bit representations, and accelerates comparisons with AVX-512 and Arm SVE SIMD instructions. Indexes can be memory-mapped and served straight from disk, and search traversal accepts custom filtering predicates. Bindings exist for Python, JavaScript, Java, Rust, Go, C#, Swift, Objective-C, C99, and Wolfram, spanning server, mobile, and WebAssembly targets. Developed by Unum under the Apache 2.0 license, it has been adopted inside databases including ClickHouse and DuckDB and integrates with LangChain and Semantic Kernel, making it a common choice when vector search needs to live inside an application rather than run as a separate service.