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langchain/docs/docs/get_started/introduction.mdx
Jacob Lee 605c3f23e1 docs: reorg and visual refresh (#19765)
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Co-authored-by: Chester Curme <chester.curme@gmail.com>
Co-authored-by: Bagatur <baskaryan@gmail.com>
2024-04-04 00:58:36 -07:00

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---
sidebar_position: 0
sidebar_class_name: hidden
---
# Introduction
**LangChain** is a framework for developing applications powered by large language models (LLMs).
LangChain simplifies every stage of the LLM application lifecycle:
- **Development**: Build your applications using LangChain's open-source [building blocks](/docs/expression_language/) and [components](/docs/modules/). Hit the ground running using [third-party integrations](/docs/integrations/platforms/) and [Templates](/docs/templates).
- **Productionization**: Use [LangSmith](/docs/langsmith/) to inspect, monitor and evaluate your chains, so that you can continuously optimize and deploy with confidence.
- **Deployment**: Turn any chain into an API with [LangServe](/docs/langserve).
import ThemedImage from '@theme/ThemedImage';
<ThemedImage
alt="Diagram outlining the hierarchical organization of the LangChain framework, displaying the interconnected parts across multiple layers."
sources={{
light: '/svg/langchain_stack.svg',
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title="LangChain Framework Overview"
/>
Concretely, the framework consists of the following open-source libraries:
- **`langchain-core`**: Base abstractions and LangChain Expression Language.
- **`langchain-community`**: Third party integrations.
- Partner packages (e.g. **`langchain-openai`**, **`langchain-anthropic`**, etc.): Some integrations have been further split into their own lightweight packages that only depend on **`langchain-core`**.
- **`langchain`**: Chains, agents, and retrieval strategies that make up an application's cognitive architecture.
- **[langgraph](/docs/langgraph)**: Build robust and stateful multi-actor applications with LLMs by modeling steps as edges and nodes in a graph.
- **[langserve](/docs/langserve)**: Deploy LangChain chains as REST APIs.
The broader ecosystem includes:
- **[LangSmith](/docs/langsmith)**: A developer platform that lets you debug, test, evaluate, and monitor LLM applications and seamlessly integrates with LangChain.
## Get started
We recommend following our [Quickstart](/docs/get_started/quickstart) guide to familiarize yourself with the framework by building your first LangChain application.
[See here](/docs/get_started/installation) for instructions on how to install LangChain, set up your environment, and start building.
:::note
These docs focus on the Python LangChain library. [Head here](https://js.langchain.com) for docs on the JavaScript LangChain library.
:::
## Use cases
If you're looking to build something specific or are more of a hands-on learner, check out our [use-cases](/docs/use_cases).
They're walkthroughs and techniques for common end-to-end tasks, such as:
- [Question answering with RAG](/docs/use_cases/question_answering/)
- [Extracting structured output](/docs/use_cases/extraction/)
- [Chatbots](/docs/use_cases/chatbots/)
- and more!
## Expression Language
LangChain Expression Language (LCEL) is the foundation of many of LangChain's components, and is a declarative way to compose chains. LCEL was designed from day 1 to support putting prototypes in production, with no code changes, from the simplest “prompt + LLM” chain to the most complex chains.
- **[Get started](/docs/expression_language/)**: LCEL and its benefits
- **[Runnable interface](/docs/expression_language/interface)**: The standard interface for LCEL objects
- **[Primitives](/docs/expression_language/primitives)**: More on the primitives LCEL includes
- and more!
## Ecosystem
### [🦜🛠️ LangSmith](/docs/langsmith)
Trace and evaluate your language model applications and intelligent agents to help you move from prototype to production.
### [🦜🕸️ LangGraph](/docs/langgraph)
Build stateful, multi-actor applications with LLMs, built on top of (and intended to be used with) LangChain primitives.
### [🦜🏓 LangServe](/docs/langserve)
Deploy LangChain runnables and chains as REST APIs.
## [Security](/docs/security)
Read up on our [Security](/docs/security) best practices to make sure you're developing safely with LangChain.
## Additional resources
### [Components](/docs/modules/)
LangChain provides standard, extendable interfaces and integrations for many different components, including:
### [Integrations](/docs/integrations/providers/)
LangChain is part of a rich ecosystem of tools that integrate with our framework and build on top of it. Check out our growing list of [integrations](/docs/integrations/providers/).
### [Guides](/docs/guides/)
Best practices for developing with LangChain.
### [API reference](https://api.python.langchain.com)
Head to the reference section for full documentation of all classes and methods in the LangChain and LangChain Experimental Python packages.
### [Contributing](/docs/contributing)
Check out the developer's guide for guidelines on contributing and help getting your dev environment set up.