> ## Documentation Index
> Fetch the complete documentation index at: https://docs.langchain.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Retriever integrations

> Integrate with retrievers using LangChain Python.

A [retriever](/oss/python/langchain/retrieval#building-blocks) is an interface that returns documents given an unstructured query.
It is more general than a vector store.
A retriever does not need to be able to store documents, only to return (or retrieve) them.
Retrievers can be created from vector stores, but are also broad enough to include other sources.

Retrievers accept a string query as input and return a list of [`Document`](https://reference.langchain.com/python/langchain-core/documents/base/Document) objects as output.

Note that all [vector stores](/oss/python/integrations/vectorstores) can be cast to retrievers. Refer to the vector store [integration docs](/oss/python/integrations/vectorstores/) for available vector stores.
This page lists custom retrievers, implemented via subclassing BaseRetriever.

## Bring-your-own documents

The below retrievers allow you to index and search a custom corpus of documents.

| Retriever                                                                                | Self-host | Cloud offering | Package                                                                                                                                    |
| ---------------------------------------------------------------------------------------- | --------- | -------------- | ------------------------------------------------------------------------------------------------------------------------------------------ |
| [`AmazonKnowledgeBasesRetriever`](/oss/python/integrations/retrievers/bedrock)           | ❌         | ✅              | [`langchain-aws`](https://reference.langchain.com/python/langchain-aws/retrievers/bedrock/AmazonKnowledgeBasesRetriever)                   |
| [`ElasticsearchRetriever`](/oss/python/integrations/retrievers/elasticsearch_retriever)  | ✅         | ✅              | [`langchain-elasticsearch`](https://reference.langchain.com/python/langchain-elasticsearch/retrievers/ElasticsearchRetriever)              |
| [`NVIDIARAGRetriever`](/oss/python/integrations/retrievers/nvidia)                       | ✅         | ❌              | [`langchain-nvidia-ai-endpoints`](https://reference.langchain.com/python/langchain-nvidia-ai-endpoints/retrievers/NVIDIARAGRetriever)      |
| [`VertexAISearchRetriever`](/oss/python/integrations/retrievers/google_vertex_ai_search) | ❌         | ✅              | [`langchain-google-community`](https://reference.langchain.com/python/langchain-google-community/vertex_ai_search/VertexAISearchRetriever) |

## External index

The below retrievers will search over an external index (e.g., constructed from Internet data or similar).

| Retriever                                                                            | Source                                                                                             | Package                                                                                                                    |
| ------------------------------------------------------------------------------------ | -------------------------------------------------------------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------- |
| [`ParallelSearchRetriever`](/oss/python/integrations/retrievers/parallel)            | Internet search via the [Parallel Search API](https://docs.parallel.ai/search/search-quickstart)   | [`langchain-parallel`](https://reference.langchain.com/python/langchain-parallel/retrievers/ParallelSearchRetriever)       |
| [`PerplexitySearchRetriever`](/oss/python/integrations/retrievers/perplexity_search) | Internet search via the [Perplexity Search API](https://docs.perplexity.ai/docs/search/quickstart) | [`langchain-perplexity`](https://reference.langchain.com/python/langchain-perplexity/retrievers/PerplexitySearchRetriever) |
| [`YouRetriever`](/oss/python/integrations/retrievers/you-retriever)                  | Internet search                                                                                    | [`langchain-youdotcom`](https://pypi.org/project/langchain-youdotcom/)                                                     |

## All retrievers

<Columns cols={3}>
  <Card title="AgentMail" icon="link" href="/oss/python/integrations/retrievers/agentmail" arrow="true" cta="View guide" />

  <Card title="Bedrock (Knowledge Bases)" icon="link" href="/oss/python/integrations/retrievers/bedrock" arrow="true" cta="View guide" />

  <Card title="Box" icon="link" href="/oss/python/integrations/retrievers/box" arrow="true" cta="View guide" />

  <Card title="Cognee" icon="link" href="/oss/python/integrations/retrievers/cognee" arrow="true" cta="View guide" />

  <Card title="Cohere reranker" icon="link" href="/oss/python/integrations/retrievers/cohere-reranker" arrow="true" cta="View guide" />

  <Card title="Cohere RAG" icon="link" href="/oss/python/integrations/retrievers/cohere" arrow="true" cta="View guide" />

  <Card title="Contextual AI Reranker" icon="link" href="/oss/python/integrations/retrievers/contextual" arrow="true" cta="View guide" />

  <Card title="Dappier" icon="link" href="/oss/python/integrations/retrievers/dappier" arrow="true" cta="View guide" />

  <Card title="Elasticsearch" icon="link" href="/oss/python/integrations/retrievers/elasticsearch_retriever" arrow="true" cta="View guide" />

  <Card title="Egnyte" icon="link" href="/oss/python/integrations/retrievers/egnyte" arrow="true" cta="View guide" />

  <Card title="Galaxia" icon="link" href="/oss/python/integrations/retrievers/galaxia-retriever" arrow="true" cta="View guide" />

  <Card title="Google Drive" icon="link" href="/oss/python/integrations/retrievers/google_drive" arrow="true" cta="View guide" />

  <Card title="Google Vertex AI Search" icon="link" href="/oss/python/integrations/retrievers/google_vertex_ai_search" arrow="true" cta="View guide" />

  <Card title="Graph RAG" icon="link" href="/oss/python/integrations/retrievers/graph_rag" arrow="true" cta="View guide" />

  <Card title="GreenNode" icon="link" href="/oss/python/integrations/retrievers/greennode_reranker" arrow="true" cta="View guide" />

  <Card title="IBM watsonx.ai" icon="link" href="/oss/python/integrations/retrievers/ibm_watsonx_ranker" arrow="true" cta="View guide" />

  <Card title="IMAP" icon="link" href="/oss/python/integrations/retrievers/imap" arrow="true" cta="View guide" />

  <Card title="Kinetica Vectorstore" icon="link" href="/oss/python/integrations/retrievers/kinetica" arrow="true" cta="View guide" />

  <Card title="LinkupSearchRetriever" icon="link" href="/oss/python/integrations/retrievers/linkup_search" arrow="true" cta="View guide" />

  <Card title="Nebius" icon="link" href="/oss/python/integrations/retrievers/nebius" arrow="true" cta="View guide" />

  <Card title="Nimble Extract" icon="link" href="/oss/python/integrations/retrievers/nimble_extract" arrow="true" cta="View guide" />

  <Card title="Nimble Search" icon="link" href="/oss/python/integrations/retrievers/nimble_search" arrow="true" cta="View guide" />

  <Card title="NVIDIA RAG Blueprint" icon="link" href="/oss/python/integrations/retrievers/nvidia" arrow="true" cta="View guide" />

  <Card title="Parallel Search" icon="link" href="/oss/python/integrations/retrievers/parallel" arrow="true" cta="View guide" />

  <Card title="Permit" icon="link" href="/oss/python/integrations/retrievers/permit" arrow="true" cta="View guide" />

  <Card title="Perigon" icon="link" href="/oss/python/integrations/retrievers/perigon" arrow="true" cta="View guide" />

  <Card title="Perplexity Search" icon="link" href="/oss/python/integrations/retrievers/perplexity_search" arrow="true" cta="View guide" />

  <Card title="Pinecone Rerank" icon="link" href="/oss/python/integrations/retrievers/pinecone_rerank" arrow="true" cta="View guide" />

  <Card title="RAGatouille" icon="link" href="/oss/python/integrations/retrievers/ragatouille" arrow="true" cta="View guide" />

  <Card title="SpiceDB" icon="link" href="/oss/python/integrations/retrievers/spicedb" arrow="true" cta="View guide" />

  <Card title="ValyuContext" icon="link" href="/oss/python/integrations/retrievers/valyu" arrow="true" cta="View guide" />

  <Card title="Vectorize" icon="link" href="/oss/python/integrations/retrievers/vectorize" arrow="true" cta="View guide" />

  <Card title="You.com" icon="link" href="/oss/python/integrations/retrievers/you-retriever" arrow="true" cta="View guide" />

  <Card title="Zotero" icon="link" href="/oss/python/integrations/retrievers/zotero" arrow="true" cta="View guide" />
</Columns>

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