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*   [Introduction](/v0.2/docs/introduction)
*   [Tutorials](/v0.2/docs/tutorials/)
    
    *   [Build a Question Answering application over a Graph Database](/v0.2/docs/tutorials/graph)
    *   [Tutorials](/v0.2/docs/tutorials/)
    *   [Build a Simple LLM Application](/v0.2/docs/tutorials/llm_chain)
    *   [Build a Query Analysis System](/v0.2/docs/tutorials/query_analysis)
    *   [Build a Chatbot](/v0.2/docs/tutorials/chatbot)
    *   [Build an Agent](/v0.2/docs/tutorials/agents)
    *   [Build an Extraction Chain](/v0.2/docs/tutorials/extraction)
    *   [Summarize Text](/v0.2/docs/tutorials/summarization)
    *   [Tagging](/v0.2/docs/tutorials/classification)
    *   [Build a Local RAG Application](/v0.2/docs/tutorials/local_rag)
    *   [Conversational RAG](/v0.2/docs/tutorials/qa_chat_history)
    *   [Build a Retrieval Augmented Generation (RAG) App](/v0.2/docs/tutorials/rag)
    *   [Build a Question/Answering system over SQL data](/v0.2/docs/tutorials/sql_qa)
*   [How-to guides](/v0.2/docs/how_to/)
    
    *   [How-to guides](/v0.2/docs/how_to/)
    *   [How to use example selectors](/v0.2/docs/how_to/example_selectors)
    *   [Installation](/v0.2/docs/how_to/installation)
    *   [How to stream responses from an LLM](/v0.2/docs/how_to/streaming_llm)
    *   [How to stream chat model responses](/v0.2/docs/how_to/chat_streaming)
    *   [How to embed text data](/v0.2/docs/how_to/embed_text)
    *   [How to use few shot examples in chat models](/v0.2/docs/how_to/few_shot_examples_chat)
    *   [How to cache model responses](/v0.2/docs/how_to/llm_caching)
    *   [How to cache chat model responses](/v0.2/docs/how_to/chat_model_caching)
    *   [How to create a custom LLM class](/v0.2/docs/how_to/custom_llm)
    *   [How to use few shot examples](/v0.2/docs/how_to/few_shot_examples)
    *   [How to use output parsers to parse an LLM response into structured format](/v0.2/docs/how_to/output_parser_structured)
    *   [How to return structured data from a model](/v0.2/docs/how_to/structured_output)
    *   [How to add ad-hoc tool calling capability to LLMs and Chat Models](/v0.2/docs/how_to/tools_prompting)
    *   [How to create a custom chat model class](/v0.2/docs/how_to/custom_chat)
    *   [How to do per-user retrieval](/v0.2/docs/how_to/qa_per_user)
    *   [How to track token usage](/v0.2/docs/how_to/chat_token_usage_tracking)
    *   [How to track token usage](/v0.2/docs/how_to/llm_token_usage_tracking)
    *   [How to pass through arguments from one step to the next](/v0.2/docs/how_to/passthrough)
    *   [How to compose prompts together](/v0.2/docs/how_to/prompts_composition)
    *   [How to use legacy LangChain Agents (AgentExecutor)](/v0.2/docs/how_to/agent_executor)
    *   [How to add values to a chain's state](/v0.2/docs/how_to/assign)
    *   [How to attach runtime arguments to a Runnable](/v0.2/docs/how_to/binding)
    *   [How to cache embedding results](/v0.2/docs/how_to/caching_embeddings)
    *   [How to split by character](/v0.2/docs/how_to/character_text_splitter)
    *   [How to manage memory](/v0.2/docs/how_to/chatbots_memory)
    *   [How to do retrieval](/v0.2/docs/how_to/chatbots_retrieval)
    *   [How to use tools](/v0.2/docs/how_to/chatbots_tools)
    *   [How to split code](/v0.2/docs/how_to/code_splitter)
    *   [How to do retrieval with contextual compression](/v0.2/docs/how_to/contextual_compression)
    *   [How to write a custom retriever class](/v0.2/docs/how_to/custom_retriever)
    *   [How to create custom Tools](/v0.2/docs/how_to/custom_tools)
    *   [How to debug your LLM apps](/v0.2/docs/how_to/debugging)
    *   [How to load CSV data](/v0.2/docs/how_to/document_loader_csv)
    *   [How to write a custom document loader](/v0.2/docs/how_to/document_loader_custom)
    *   [How to load data from a directory](/v0.2/docs/how_to/document_loader_directory)
    *   [How to load PDF files](/v0.2/docs/how_to/document_loader_pdf)
    *   [How to load JSON data](/v0.2/docs/how_to/document_loaders_json)
    *   [How to select examples by length](/v0.2/docs/how_to/example_selectors_length_based)
    *   [How to select examples by similarity](/v0.2/docs/how_to/example_selectors_similarity)
    *   [How to use reference examples](/v0.2/docs/how_to/extraction_examples)
    *   [How to handle long text](/v0.2/docs/how_to/extraction_long_text)
    *   [How to do extraction without using function calling](/v0.2/docs/how_to/extraction_parse)
    *   [Fallbacks](/v0.2/docs/how_to/fallbacks)
    *   [Few Shot Prompt Templates](/v0.2/docs/how_to/few_shot)
    *   [How to run custom functions](/v0.2/docs/how_to/functions)
    *   [How to construct knowledge graphs](/v0.2/docs/how_to/graph_constructing)
    *   [How to map values to a database](/v0.2/docs/how_to/graph_mapping)
    *   [How to improve results with prompting](/v0.2/docs/how_to/graph_prompting)
    *   [How to add a semantic layer over the database](/v0.2/docs/how_to/graph_semantic)
    *   [How to reindex data to keep your vectorstore in-sync with the underlying data source](/v0.2/docs/how_to/indexing)
    *   [How to get log probabilities](/v0.2/docs/how_to/logprobs)
    *   [How to add message history](/v0.2/docs/how_to/message_history)
    *   [How to generate multiple embeddings per document](/v0.2/docs/how_to/multi_vector)
    *   [How to generate multiple queries to retrieve data for](/v0.2/docs/how_to/multiple_queries)
    *   [How to parse JSON output](/v0.2/docs/how_to/output_parser_json)
    *   [How to retry when output parsing errors occur](/v0.2/docs/how_to/output_parser_retry)
    *   [How to parse XML output](/v0.2/docs/how_to/output_parser_xml)
    *   [How to invoke runnables in parallel](/v0.2/docs/how_to/parallel)
    *   [How to retrieve the whole document for a chunk](/v0.2/docs/how_to/parent_document_retriever)
    *   [How to partially format prompt templates](/v0.2/docs/how_to/prompts_partial)
    *   [How to add chat history to a question-answering chain](/v0.2/docs/how_to/qa_chat_history_how_to)
    *   [How to return citations](/v0.2/docs/how_to/qa_citations)
    *   [How to return sources](/v0.2/docs/how_to/qa_sources)
    *   [How to stream from a question-answering chain](/v0.2/docs/how_to/qa_streaming)
    *   [How to construct filters](/v0.2/docs/how_to/query_constructing_filters)
    *   [How to add examples to the prompt](/v0.2/docs/how_to/query_few_shot)
    *   [How to deal with high cardinality categorical variables](/v0.2/docs/how_to/query_high_cardinality)
    *   [How to handle multiple queries](/v0.2/docs/how_to/query_multiple_queries)
    *   [How to handle multiple retrievers](/v0.2/docs/how_to/query_multiple_retrievers)
    *   [How to handle cases where no queries are generated](/v0.2/docs/how_to/query_no_queries)
    *   [How to recursively split text by characters](/v0.2/docs/how_to/recursive_text_splitter)
    *   [How to reduce retrieval latency](/v0.2/docs/how_to/reduce_retrieval_latency)
    *   [How to route execution within a chain](/v0.2/docs/how_to/routing)
    *   [How to chain runnables](/v0.2/docs/how_to/sequence)
    *   [How to split text by tokens](/v0.2/docs/how_to/split_by_token)
    *   [How to deal with large databases](/v0.2/docs/how_to/sql_large_db)
    *   [How to use prompting to improve results](/v0.2/docs/how_to/sql_prompting)
    *   [How to do query validation](/v0.2/docs/how_to/sql_query_checking)
    *   [How to stream](/v0.2/docs/how_to/streaming)
    *   [How to create a time-weighted retriever](/v0.2/docs/how_to/time_weighted_vectorstore)
    *   [How to use a chat model to call tools](/v0.2/docs/how_to/tool_calling)
    *   [How to call tools with multi-modal data](/v0.2/docs/how_to/tool_calls_multi_modal)
    *   [How to use LangChain tools](/v0.2/docs/how_to/tools_builtin)
    *   [How use a vector store to retrieve data](/v0.2/docs/how_to/vectorstore_retriever)
    *   [How to create and query vector stores](/v0.2/docs/how_to/vectorstores)
*   [Conceptual guide](/v0.2/docs/concepts)
*   Ecosystem
    
    *   [🦜🛠️ LangSmith](/v0.2/docs/langsmith/)
        
    *   [🦜🕸️LangGraph.js](/v0.2/docs/langgraph)
*   Versions
    
    *   [Overview](/v0.2/docs/versions/overview)
    *   [v0.2](/v0.2/docs/versions/v0_2)
    *   [Release Policy](/v0.2/docs/versions/release_policy)
    *   [Packages](/v0.2/docs/versions/packages)
*   [Security](/v0.2/docs/security)

*   [](/v0.2/)
*   [Tutorials](/v0.2/docs/tutorials/)
*   Summarize Text

Summarize Text
==============

A common use case is wanting to summarize long documents. This naturally runs into the context window limitations. Unlike in question-answering, you can't just do some semantic search hacks to only select the chunks of text most relevant to the question (because, in this case, there is no particular question - you want to summarize everything). So what do you do then?

To get started, we would recommend checking out the summarization chain, which attacks this problem in a recursive manner.

*   [Summarization Chain](https://js.langchain.com/v0.1/docs/modules/chains/popular/summarize)

Example[​](#example "Direct link to Example")
---------------------------------------------

Here's an example of how you can use the [RefineDocumentsChain](https://js.langchain.com/v0.1/docs/modules/chains/document/refine) to summarize documents loaded from a YouTube video:

tip

See [this section for general instructions on installing integration packages](/v0.2/docs/how_to/installation#installing-integration-packages).

*   npm
*   Yarn
*   pnpm

    npm install @langchain/anthropic

    yarn add @langchain/anthropic

    pnpm add @langchain/anthropic

    import { loadSummarizationChain } from "langchain/chains";import { SearchApiLoader } from "langchain/document_loaders/web/searchapi";import { TokenTextSplitter } from "@langchain/textsplitters";import { PromptTemplate } from "@langchain/core/prompts";import { ChatAnthropic } from "@langchain/anthropic";const loader = new SearchApiLoader({  engine: "youtube_transcripts",  video_id: "WTOm65IZneg",});const docs = await loader.load();const splitter = new TokenTextSplitter({  chunkSize: 10000,  chunkOverlap: 250,});const docsSummary = await splitter.splitDocuments(docs);const llmSummary = new ChatAnthropic({  model: "claude-3-sonnet-20240229",  temperature: 0.3,});const summaryTemplate = `You are an expert in summarizing YouTube videos.Your goal is to create a summary of a podcast.Below you find the transcript of a podcast:--------{text}--------The transcript of the podcast will also be used as the basis for a question and answer bot.Provide some examples questions and answers that could be asked about the podcast. Make these questions very specific.Total output will be a summary of the video and a list of example questions the user could ask of the video.SUMMARY AND QUESTIONS:`;const SUMMARY_PROMPT = PromptTemplate.fromTemplate(summaryTemplate);const summaryRefineTemplate = `You are an expert in summarizing YouTube videos.Your goal is to create a summary of a podcast.We have provided an existing summary up to a certain point: {existing_answer}Below you find the transcript of a podcast:--------{text}--------Given the new context, refine the summary and example questions.The transcript of the podcast will also be used as the basis for a question and answer bot.Provide some examples questions and answers that could be asked about the podcast. Makethese questions very specific.If the context isn't useful, return the original summary and questions.Total output will be a summary of the video and a list of example questions the user could ask of the video.SUMMARY AND QUESTIONS:`;const SUMMARY_REFINE_PROMPT = PromptTemplate.fromTemplate(  summaryRefineTemplate);const summarizeChain = loadSummarizationChain(llmSummary, {  type: "refine",  verbose: true,  questionPrompt: SUMMARY_PROMPT,  refinePrompt: SUMMARY_REFINE_PROMPT,});const summary = await summarizeChain.run(docsSummary);console.log(summary);/*  Here is a summary of the key points from the podcast transcript:  - Jimmy helps provide hearing aids and cochlear implants to deaf and hard-of-hearing people who can't afford them. He helps over 1,000 people hear again.  - Jimmy surprises recipients with $10,000 cash gifts in addition to the hearing aids. He also gifts things like jet skis, basketball game tickets, and trips to concerts.  - Jimmy travels internationally to provide hearing aids, visiting places like Mexico, Guatemala, Brazil, South Africa, Malawi, and Indonesia.   - Jimmy donates $100,000 to organizations around the world that teach sign language.  - The recipients are very emotional and grateful to be able to hear their loved ones again.  Here are some example questions and answers about the podcast:  Q: How many people did Jimmy help regain their hearing?  A: Jimmy helped over 1,000 people regain their hearing.  Q: What types of hearing devices did Jimmy provide to the recipients?  A: Jimmy provided cutting-edge hearing aids and cochlear implants.  Q: In addition to the hearing devices, what surprise gifts did Jimmy give some recipients?  A: In addition to hearing devices, Jimmy surprised some recipients with $10,000 cash gifts, jet skis, basketball game tickets, and concert tickets.  Q: What countries did Jimmy travel to in order to help people?  A: Jimmy traveled to places like Mexico, Guatemala, Brazil, South Africa, Malawi, and Indonesia.  Q: How much money did Jimmy donate to organizations that teach sign language?  A: Jimmy donated $100,000 to sign language organizations around the world.  Q: How did the recipients react when they were able to hear again?  A: The recipients were very emotional and grateful, with many crying tears of joy at being able to hear their loved ones again.*/

#### API Reference:

*   [loadSummarizationChain](https://v02.api.js.langchain.com/functions/langchain_chains.loadSummarizationChain.html) from `langchain/chains`
*   [SearchApiLoader](https://v02.api.js.langchain.com/classes/langchain_document_loaders_web_searchapi.SearchApiLoader.html) from `langchain/document_loaders/web/searchapi`
*   [TokenTextSplitter](https://v02.api.js.langchain.com/classes/langchain_textsplitters.TokenTextSplitter.html) from `@langchain/textsplitters`
*   [PromptTemplate](https://v02.api.js.langchain.com/classes/langchain_core_prompts.PromptTemplate.html) from `@langchain/core/prompts`
*   [ChatAnthropic](https://v02.api.js.langchain.com/classes/langchain_anthropic.ChatAnthropic.html) from `@langchain/anthropic`

* * *

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