Citations

This feature is eligible for Zero Data Retention (ZDR). When your organization has a ZDR arrangement, data sent through this feature is not stored after the API response is returned.

Claude is capable of providing detailed citations when answering questions about documents, helping you track and verify information sources in responses. All active models support citations, with the exception of Haiku 3.

Share your feedback and suggestions about the citations feature using this form.

Here’s an example of how to use citations with the Messages API:

curl https://api.anthropic.com/v1/messages \
  -H "content-type: application/json" \
  -H "x-api-key: $ANTHROPIC_API_KEY" \
  -H "anthropic-version: 2023-06-01" \
  -d '{
    "model": "claude-opus-4-7",
    "max_tokens": 1024,
    "messages": [
      {
        "role": "user",
        "content": [
          {
            "type": "document",
            "source": {
              "type": "text",
              "media_type": "text/plain",
              "data": "The grass is green. The sky is blue."
            },
            "title": "My Document",
            "context": "This is a trustworthy document.",
            "citations": {"enabled": true}
          },
          {
            "type": "text",
            "text": "What color is the grass and sky?"
          }
        ]
      }
    ]
  }'

ant messages create <<'YAML'
model: claude-opus-4-7
max_tokens: 1024
messages:
  - role: user
    content:
      - type: document
        source:
          type: text
          media_type: text/plain
          data: The grass is green. The sky is blue.
        title: My Document
        context: This is a trustworthy document.
        citations:
          enabled: true
      - type: text
        text: What color is the grass and sky?
YAML

import anthropic

client = anthropic.Anthropic()

response = client.messages.create(
    model="claude-opus-4-7",
    max_tokens=1024,
    messages=[
        {
            "role": "user",
            "content": [
                {
                    "type": "document",
                    "source": {
                        "type": "text",
                        "media_type": "text/plain",
                        "data": "The grass is green. The sky is blue.",
                    },
                    "title": "My Document",
                    "context": "This is a trustworthy document.",
                    "citations": {"enabled": True},
                },
                {"type": "text", "text": "What color is the grass and sky?"},
            ],
        }
    ],
)
print(response)

import com.anthropic.client.AnthropicClient;
import com.anthropic.client.okhttp.AnthropicOkHttpClient;
import com.anthropic.models.messages.*;
import java.util.List;

public class DocumentExample {

  public static void main(String[] args) {
    AnthropicClient client = AnthropicOkHttpClient.fromEnv();

    PlainTextSource source = PlainTextSource.builder()
      .data("The grass is green. The sky is blue.")
      .build();

    DocumentBlockParam documentParam = DocumentBlockParam.builder()
      .source(source)
      .title("My Document")
      .context("This is a trustworthy document.")
      .citations(CitationsConfigParam.builder().enabled(true).build())
      .build();

    TextBlockParam textBlockParam = TextBlockParam.builder()
      .text("What color is the grass and sky?")
      .build();

    MessageCreateParams params = MessageCreateParams.builder()
      .model(Model.CLAUDE_OPUS_4_7)
      .maxTokens(1024)
      .addUserMessageOfBlockParams(
        List.of(
          ContentBlockParam.ofDocument(documentParam),
          ContentBlockParam.ofText(textBlockParam)
        )
      )
      .build();

    Message message = client.messages().create(params);
    System.out.println(message);
  }
}

Comparison with prompt-based approachesIn comparison with prompt-based citations solutions, the citations feature has the following advantages:

Cost savings: If your prompt-based approach asks Claude to output direct quotes, you may see cost savings due to the fact that cited_text does not count towards your output tokens.
Better citation reliability: Because citations are parsed into the respective response formats mentioned above and cited_text is extracted, citations are guaranteed to contain valid pointers to the provided documents.
Improved citation quality: In evaluations, the citations feature was found to be significantly more likely to cite the most relevant quotes from documents as compared to purely prompt-based approaches.

How citations work

Integrate citations with Claude in these steps:

Provide document(s) and enable citations

Include documents in any of the supported formats: PDFs, plain text, or custom content documents
Set citations.enabled=true on each of your documents. Currently, citations must be enabled on all or none of the documents within a request.
Note that only text citations are currently supported and image citations are not yet possible.

Documents get processed

Document contents are “chunked” in order to define the minimum granularity of possible citations. For example, sentence chunking would allow Claude to cite a single sentence or chain together multiple consecutive sentences to cite a paragraph (or longer)!
- For PDFs: Text is extracted as described in PDF Support and content is chunked into sentences. Citing images from PDFs is not currently supported.
- For plain text documents: Content is chunked into sentences that can be cited from.
- For custom content documents: Your provided content blocks are used as-is and no further chunking is done.

Claude provides cited response

Responses may now include multiple text blocks where each text block can contain a claim that Claude is making and a list of citations that support the claim.
Citations reference specific locations in source documents. The format of these citations are dependent on the type of document being cited from.
- For PDFs: Citations include the page number range (1-indexed).
- For plain text documents: Citations include the character index range (0-indexed).
- For custom content documents: Citations include the content block index range (0-indexed) corresponding to the original content list provided.
Document indices are provided to indicate the reference source and are 0-indexed according to the list of all documents in your original request.

Automatic chunking vs custom contentBy default, plain text and PDF documents are automatically chunked into sentences. If you need more control over citation granularity (e.g., for bullet points or transcripts), use custom content documents instead. See Document Types for more details.For example, if you want Claude to be able to cite specific sentences from your RAG chunks, you should put each RAG chunk into a plain text document. Otherwise, if you do not want any further chunking to be done, or if you want to customize any additional chunking, you can put RAG chunks into custom content document(s).

Citable vs non-citable content

Text found within a document’s source content can be cited from.
title and context are optional fields that will be passed to the model but not used towards cited content.
title is limited in length so you may find the context field to be useful in storing any document metadata as text or stringified json.

Citation indices

Document indices are 0-indexed from the list of all document content blocks in the request (spanning across all messages).
Character indices are 0-indexed with exclusive end indices.
Page numbers are 1-indexed with exclusive end page numbers.
Content block indices are 0-indexed with exclusive end indices from the content list provided in the custom content document.

Token costs

Enabling citations incurs a slight increase in input tokens due to system prompt additions and document chunking.
However, the citations feature is very efficient with output tokens. Under the hood, the model is outputting citations in a standardized format that are then parsed into cited text and document location indices. The cited_text field is provided for convenience and does not count towards output tokens.
When passed back in subsequent conversation turns, cited_text is also not counted towards input tokens.

Feature compatibility

Citations works in conjunction with other API features including prompt caching, token counting and batch processing.

Citations and Structured Outputs are incompatibleCitations cannot be used together with Structured Outputs. If you enable citations on any user-provided document (Document blocks or RequestSearchResultBlock) and also include the output_config.format parameter (or the deprecated output_format parameter), the API will return a 400 error.This is because citations require interleaving citation blocks with text output, which is incompatible with the strict JSON schema constraints of structured outputs.

Using Prompt Caching with Citations

Citations and prompt caching can be used together effectively. The citation blocks generated in responses cannot be cached directly, but the source documents they reference can be cached. To optimize performance, apply cache_control to your top-level document content blocks.

curl https://api.anthropic.com/v1/messages \
     --header "x-api-key: $ANTHROPIC_API_KEY" \
     --header "anthropic-version: 2023-06-01" \
     --header "content-type: application/json" \
     --data '{
    "model": "claude-opus-4-7",
    "max_tokens": 1024,
    "messages": [
        {
            "role": "user",
            "content": [
                {
                    "type": "document",
                    "source": {
                        "type": "text",
                        "media_type": "text/plain",
                        "data": "This is a very long document with thousands of words..."
                    },
                    "citations": {"enabled": true},
                    "cache_control": {"type": "ephemeral"}
                },
                {
                    "type": "text",
                    "text": "What does this document say about API features?"
                }
            ]
        }
    ]
}'

ant messages create \
  --model claude-opus-4-7 \
  --max-tokens 1024 <<'YAML'
messages:
  - role: user
    content:
      - type: document
        source:
          type: text
          media_type: text/plain
          data: This is a very long document with thousands of words...
        citations:
          enabled: true
        cache_control:
          type: ephemeral
      - type: text
        text: What does this document say about API features?
YAML

import anthropic

client = anthropic.Anthropic()

# Long document content (e.g., technical documentation)
long_document = (
    "This is a very long document with thousands of words..." + " ... " * 1000
)  # Minimum cacheable length

response = client.messages.create(
    model="claude-opus-4-7",
    max_tokens=1024,
    messages=[
        {
            "role": "user",
            "content": [
                {
                    "type": "document",
                    "source": {
                        "type": "text",
                        "media_type": "text/plain",
                        "data": long_document,
                    },
                    "citations": {"enabled": True},
                    "cache_control": {
                        "type": "ephemeral"
                    },  # Cache the document content
                },
                {
                    "type": "text",
                    "text": "What does this document say about API features?",
                },
            ],
        }
    ],
)
print(response)

import Anthropic from "@anthropic-ai/sdk";

const client = new Anthropic();

// Long document content (e.g., technical documentation)
const longDocument =
  "This is a very long document with thousands of words..." + " ... ".repeat(1000); // Minimum cacheable length

const response = await client.messages.create({
  model: "claude-opus-4-7",
  max_tokens: 1024,
  messages: [
    {
      role: "user",
      content: [
        {
          type: "document",
          source: {
            type: "text",
            media_type: "text/plain",
            data: longDocument
          },
          citations: { enabled: true },
          cache_control: { type: "ephemeral" } // Cache the document content
        },
        {
          type: "text",
          text: "What does this document say about API features?"
        }
      ]
    }
  ]
});

In this example:

The document content is cached using cache_control on the document block
Citations are enabled on the document
Claude can generate responses with citations while benefiting from cached document content
Subsequent requests using the same document will benefit from the cached content

Document Types

Choosing a document type

Three document types are supported for citations. Documents can be provided directly in the message (base64, text, or URL) or uploaded via the Files API and referenced by file_id:

Type	Best for	Chunking	Citation format
Plain text	Simple text documents, prose	Sentence	Character indices (0-indexed)
PDF	PDF files with text content	Sentence	Page numbers (1-indexed)
Custom content	Lists, transcripts, special formatting, more granular citations	No additional chunking	Block indices (0-indexed)

.csv, .xlsx, .docx, .md, and .txt files are not supported as document blocks. Convert these to plain text and include directly in message content. See Working with other file formats.

Plain text documents

Plain text documents are automatically chunked into sentences. You can provide them inline or by reference with their file_id:

Inline text
Files API

{
    "type": "document",
    "source": {
        "type": "text",
        "media_type": "text/plain",
        "data": "Plain text content...",
    },
    "title": "Document Title",  # optional
    "context": "Context about the document that will not be cited from",  # optional
    "citations": {"enabled": True},
}

{
    "type": "document",
    "source": {"type": "file", "file_id": "file_011CNvxoj286tYUAZFiZMf1U"},
    "title": "Document Title",  # optional
    "context": "Context about the document that will not be cited from",  # optional
    "citations": {"enabled": True},
}

{
    "type": "char_location",
    "cited_text": "The exact text being cited",  # not counted towards output tokens
    "document_index": 0,
    "document_title": "Document Title",
    "start_char_index": 0,  # 0-indexed
    "end_char_index": 50,  # exclusive
}

PDF documents

PDF documents can be provided as base64-encoded data or by file_id. PDF text is extracted and chunked into sentences. As image citations are not yet supported, PDFs that are scans of documents and do not contain extractable text will not be citable.

Base64
Files API

{
    "type": "document",
    "source": {
        "type": "base64",
        "media_type": "application/pdf",
        "data": base64_encoded_pdf_data,
    },
    "title": "Document Title",  # optional
    "context": "Context about the document that will not be cited from",  # optional
    "citations": {"enabled": True},
}

{
    "type": "document",
    "source": {"type": "file", "file_id": "file_011CNvxoj286tYUAZFiZMf1U"},
    "title": "Document Title",  # optional
    "context": "Context about the document that will not be cited from",  # optional
    "citations": {"enabled": True},
}

{
    "type": "page_location",
    "cited_text": "The exact text being cited",  # not counted towards output tokens
    "document_index": 0,
    "document_title": "Document Title",
    "start_page_number": 1,  # 1-indexed
    "end_page_number": 2,  # exclusive
}

Custom content documents

Custom content documents give you control over citation granularity. No additional chunking is done and chunks are provided to the model according to the content blocks provided.

{
    "type": "document",
    "source": {
        "type": "content",
        "content": [
            {"type": "text", "text": "First chunk"},
            {"type": "text", "text": "Second chunk"},
        ],
    },
    "title": "Document Title",  # optional
    "context": "Context about the document that will not be cited from",  # optional
    "citations": {"enabled": True},
}

{
    "type": "content_block_location",
    "cited_text": "The exact text being cited",  # not counted towards output tokens
    "document_index": 0,
    "document_title": "Document Title",
    "start_block_index": 0,  # 0-indexed
    "end_block_index": 1,  # exclusive
}

Response Structure

When citations are enabled, responses include multiple text blocks with citations:

{
    "content": [
        {"type": "text", "text": "According to the document, "},
        {
            "type": "text",
            "text": "the grass is green",
            "citations": [
                {
                    "type": "char_location",
                    "cited_text": "The grass is green.",
                    "document_index": 0,
                    "document_title": "Example Document",
                    "start_char_index": 0,
                    "end_char_index": 20,
                }
            ],
        },
        {"type": "text", "text": " and "},
        {
            "type": "text",
            "text": "the sky is blue",
            "citations": [
                {
                    "type": "char_location",
                    "cited_text": "The sky is blue.",
                    "document_index": 0,
                    "document_title": "Example Document",
                    "start_char_index": 20,
                    "end_char_index": 36,
                }
            ],
        },
        {
            "type": "text",
            "text": ". Information from page 5 states that ",
        },
        {
            "type": "text",
            "text": "water is essential",
            "citations": [
                {
                    "type": "page_location",
                    "cited_text": "Water is essential for life.",
                    "document_index": 1,
                    "document_title": "PDF Document",
                    "start_page_number": 5,
                    "end_page_number": 6,
                }
            ],
        },
        {
            "type": "text",
            "text": ". The custom document mentions ",
        },
        {
            "type": "text",
            "text": "important findings",
            "citations": [
                {
                    "type": "content_block_location",
                    "cited_text": "These are important findings.",
                    "document_index": 2,
                    "document_title": "Custom Content Document",
                    "start_block_index": 0,
                    "end_block_index": 1,
                }
            ],
        },
    ]
}

Streaming Support

For streaming responses, a citations_delta type is included that contains a single citation to be added to the citations list on the current text content block.

event: message_start
data: {"type": "message_start", ...}

event: content_block_start
data: {"type": "content_block_start", "index": 0, ...}

event: content_block_delta
data: {"type": "content_block_delta", "index": 0,
       "delta": {"type": "text_delta", "text": "According to..."}}

event: content_block_delta
data: {"type": "content_block_delta", "index": 0,
       "delta": {"type": "citations_delta",
                 "citation": {
                     "type": "char_location",
                     "cited_text": "...",
                     "document_index": 0,
                     ...
                 }}}

event: content_block_stop
data: {"type": "content_block_stop", "index": 0}

event: message_stop
data: {"type": "message_stop"}

Product Guide

Account

Help

Citations

Citations

How citations work

Citable vs non-citable content

Citation indices

Token costs

Feature compatibility

Using Prompt Caching with Citations

Document Types

Choosing a document type

Plain text documents

PDF documents

Custom content documents

Response Structure

Streaming Support

​Citations

​How citations work

​Citable vs non-citable content

​Citation indices

​Token costs

​Feature compatibility

​Using Prompt Caching with Citations

​Document Types

​Choosing a document type

​Plain text documents

​PDF documents

​Custom content documents

​Response Structure

​Streaming Support

Citations

How citations work

Citable vs non-citable content

Citation indices

Token costs

Feature compatibility

Using Prompt Caching with Citations

Document Types

Choosing a document type

Plain text documents

PDF documents

Custom content documents

Response Structure

Streaming Support