Best LLM frameworks in 2026

Libraries for building apps and agents on top of language models. 2 tools, ranked by live GitHub and npm numbers.

Tool	Pricing	GitHub stars	npm a week	Last release
LangChainOpen source framework for building applications with language models, paired with the LangSmith platform.	Freemium	147k	3.8M	3 days ago
LlamaIndexOpen source data framework for connecting language models to your own data, plus a paid parsing platform.	Freemium	52.4k	160k	2 weeks ago

LLM Frameworks comparisons

LangChainvsLlamaIndex

LangChain is an open source framework for building LLM applications through chains, agents, tools and memory, paired with LangSmith, a paid observability and deployment platform.

How to choose

LLM frameworks are libraries that sit between your code and a model. They handle the repeated work: calling different providers through one interface, chaining steps, retrieving your own data for the model to read, and running agents that call tools.

They save time when an app has several steps or needs to work across providers. For a single call to one model, the provider's own SDK is often enough.

What to compare

Languages supported
Model providers and vector stores it connects to
Agent and tool-calling support
Tracing, evaluation and hosted add-ons
License and release activity

Questions

Do I need a framework to build with a language model?

No. For one prompt and one response, the provider's SDK is simpler. A framework helps once you chain several steps, retrieve your own data, run agents or want to switch providers.