LangChain, released as an open-source project by Harrison Chase in October 2022, gives developers a standard set of building blocks, chains, retrieval, memory, and tool calling, for building applications on top of large language models, rather than each team writing that plumbing from scratch.
That early, foundational position shows in its reach: LangChain and its companion agent-orchestration library LangGraph combine for roughly 90 million monthly downloads, and the company reports 35% of the Fortune 500 build on its tooling. The company raised a $125 million Series B in October 2025 at a $1.25 billion valuation, led by IVP alongside Sequoia, Benchmark, and CapitalG, on top of $260 million raised total.
The core framework is free and open source, with LangSmith, the company's separate observability and debugging product, and LangGraph Platform, its hosted deployment layer, available as paid additions for teams running agents in production. For a developer who wants proven, widely-adopted building blocks for LLM applications rather than writing the retrieval, memory, and tool-calling plumbing from scratch, LangChain's foundational library addresses that directly.
