Web search tool

The web search tool gives Claude direct access to real-time web content, allowing it to answer questions with up-to-date information beyond its knowledge cutoff. Claude automatically cites sources from search results as part of its answer.

Please reach out through our feedback form to share your experience with the web search tool.

Supported models

Web search is available on:

Claude Sonnet 4.5 (claude-sonnet-4-5-20250929)
Claude Sonnet 4 (claude-sonnet-4-20250514)
Claude Sonnet 3.7 (deprecated) (claude-3-7-sonnet-20250219)
Claude Haiku 4.5 (claude-haiku-4-5-20251001)
Claude Haiku 3.5 (claude-3-5-haiku-latest)
Claude Opus 4.5 (claude-opus-4-5-20251101)
Claude Opus 4.1 (claude-opus-4-1-20250805)
Claude Opus 4 (claude-opus-4-20250514)

How web search works

When you add the web search tool to your API request:

Claude decides when to search based on the prompt.
The API executes the searches and provides Claude with the results. This process may repeat multiple times throughout a single request.
At the end of its turn, Claude provides a final response with cited sources.

How to use web search

Your organization’s administrator must enable web search in Console.

Provide the web search tool in your API request:

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-sonnet-4-5",
        "max_tokens": 1024,
        "messages": [
            {
                "role": "user",
                "content": "What is the weather in NYC?"
            }
        ],
        "tools": [{
            "type": "web_search_20250305",
            "name": "web_search",
            "max_uses": 5
        }]
    }'

import anthropic

client = anthropic.Anthropic()

response = client.messages.create(
    model="claude-sonnet-4-5",
    max_tokens=1024,
    messages=[
        {
            "role": "user",
            "content": "What's the weather in NYC?"
        }
    ],
    tools=[{
        "type": "web_search_20250305",
        "name": "web_search",
        "max_uses": 5
    }]
)
print(response)

import { Anthropic } from '@anthropic-ai/sdk';

const anthropic = new Anthropic();

async function main() {
  const response = await anthropic.messages.create({
    model: "claude-sonnet-4-5",
    max_tokens: 1024,
    messages: [
      {
        role: "user",
        content: "What's the weather in NYC?"
      }
    ],
    tools: [{
      type: "web_search_20250305",
      name: "web_search",
      max_uses: 5
    }]
  });

  console.log(response);
}

main().catch(console.error);

Tool definition

The web search tool supports the following parameters:

JSON

{
  "type": "web_search_20250305",
  "name": "web_search",

  // Optional: Limit the number of searches per request
  "max_uses": 5,

  // Optional: Only include results from these domains
  "allowed_domains": ["example.com", "trusteddomain.org"],

  // Optional: Never include results from these domains
  "blocked_domains": ["untrustedsource.com"],

  // Optional: Localize search results
  "user_location": {
    "type": "approximate",
    "city": "San Francisco",
    "region": "California",
    "country": "US",
    "timezone": "America/Los_Angeles"
  }
}

Max uses

The max_uses parameter limits the number of searches performed. If Claude attempts more searches than allowed, the web_search_tool_result will be an error with the max_uses_exceeded error code.

Domain filtering

When using domain filters:

Domains should not include the HTTP/HTTPS scheme (use example.com instead of https://example.com)
Subdomains are automatically included (example.com covers docs.example.com)
Specific subdomains restrict results to only that subdomain (docs.example.com returns only results from that subdomain, not from example.com or api.example.com)
Subpaths are supported and match anything after the path (example.com/blog matches example.com/blog/post-1)
You can use either allowed_domains or blocked_domains, but not both in the same request.

Wildcard support:

Only one wildcard (*) is allowed per domain entry, and it must appear after the domain part (in the path)
Valid: example.com/*, example.com/*/articles
Invalid: *.example.com, ex*.com, example.com/*/news/*

Invalid domain formats will return an invalid_tool_input tool error.

Request-level domain restrictions must be compatible with organization-level domain restrictions configured in the Console. Request-level domains can only further restrict domains, not override or expand beyond the organization-level list. If your request includes domains that conflict with organization settings, the API will return a validation error.

Localization

The user_location parameter allows you to localize search results based on a user’s location.

type: The type of location (must be approximate)
city: The city name
region: The region or state
country: The country
timezone: The IANA timezone ID.

Response

Here’s an example response structure:

{
  "role": "assistant",
  "content": [
    // 1. Claude's decision to search
    {
      "type": "text",
      "text": "I'll search for when Claude Shannon was born."
    },
    // 2. The search query used
    {
      "type": "server_tool_use",
      "id": "srvtoolu_01WYG3ziw53XMcoyKL4XcZmE",
      "name": "web_search",
      "input": {
        "query": "claude shannon birth date"
      }
    },
    // 3. Search results
    {
      "type": "web_search_tool_result",
      "tool_use_id": "srvtoolu_01WYG3ziw53XMcoyKL4XcZmE",
      "content": [
        {
          "type": "web_search_result",
          "url": "https://en.wikipedia.org/wiki/Claude_Shannon",
          "title": "Claude Shannon - Wikipedia",
          "encrypted_content": "EqgfCioIARgBIiQ3YTAwMjY1Mi1mZjM5LTQ1NGUtODgxNC1kNjNjNTk1ZWI3Y...",
          "page_age": "April 30, 2025"
        }
      ]
    },
    {
      "text": "Based on the search results, ",
      "type": "text"
    },
    // 4. Claude's response with citations
    {
      "text": "Claude Shannon was born on April 30, 1916, in Petoskey, Michigan",
      "type": "text",
      "citations": [
        {
          "type": "web_search_result_location",
          "url": "https://en.wikipedia.org/wiki/Claude_Shannon",
          "title": "Claude Shannon - Wikipedia",
          "encrypted_index": "Eo8BCioIAhgBIiQyYjQ0OWJmZi1lNm..",
          "cited_text": "Claude Elwood Shannon (April 30, 1916 – February 24, 2001) was an American mathematician, electrical engineer, computer scientist, cryptographer and i..."
        }
      ]
    }
  ],
  "id": "msg_a930390d3a",
  "usage": {
    "input_tokens": 6039,
    "output_tokens": 931,
    "server_tool_use": {
      "web_search_requests": 1
    }
  },
  "stop_reason": "end_turn"
}

Search results

Search results include:

url: The URL of the source page
title: The title of the source page
page_age: When the site was last updated
encrypted_content: Encrypted content that must be passed back in multi-turn conversations for citations

Citations

Citations are always enabled for web search, and each web_search_result_location includes:

url: The URL of the cited source
title: The title of the cited source
encrypted_index: A reference that must be passed back for multi-turn conversations.
cited_text: Up to 150 characters of the cited content

The web search citation fields cited_text, title, and url do not count towards input or output token usage.

When displaying API outputs directly to end users, citations must be included to the original source. If you are making modifications to API outputs, including by reprocessing and/or combining them with your own material before displaying them to end users, display citations as appropriate based on consultation with your legal team.

Errors

When the web search tool encounters an error (such as hitting rate limits), the Claude API still returns a 200 (success) response. The error is represented within the response body using the following structure:

{
  "type": "web_search_tool_result",
  "tool_use_id": "servertoolu_a93jad",
  "content": {
    "type": "web_search_tool_result_error",
    "error_code": "max_uses_exceeded"
  }
}

These are the possible error codes:

too_many_requests: Rate limit exceeded
invalid_input: Invalid search query parameter
max_uses_exceeded: Maximum web search tool uses exceeded
query_too_long: Query exceeds maximum length
unavailable: An internal error occurred

`pause_turn` stop reason

The response may include a pause_turn stop reason, which indicates that the API paused a long-running turn. You may provide the response back as-is in a subsequent request to let Claude continue its turn, or modify the content if you wish to interrupt the conversation.

Prompt caching

Web search works with prompt caching. To enable prompt caching, add at least one cache_control breakpoint in your request. The system will automatically cache up until the last web_search_tool_result block when executing the tool. For multi-turn conversations, set a cache_control breakpoint on or after the last web_search_tool_result block to reuse cached content. For example, to use prompt caching with web search for a multi-turn conversation:

import anthropic

client = anthropic.Anthropic()

# First request with web search and cache breakpoint
messages = [
    {
        "role": "user",
        "content": "What's the current weather in San Francisco today?"
    }
]

response1 = client.messages.create(
    model="claude-sonnet-4-5",
    max_tokens=1024,
    messages=messages,
    tools=[{
        "type": "web_search_20250305",
        "name": "web_search",
        "user_location": {
            "type": "approximate",
            "city": "San Francisco",
            "region": "California",
            "country": "US",
            "timezone": "America/Los_Angeles"
        }
    }]
)

# Add Claude's response to the conversation
messages.append({
    "role": "assistant",
    "content": response1.content
})

# Second request with cache breakpoint after the search results
messages.append({
    "role": "user",
    "content": "Should I expect rain later this week?",
    "cache_control": {"type": "ephemeral"}  # Cache up to this point
})

response2 = client.messages.create(
    model="claude-sonnet-4-5",
    max_tokens=1024,
    messages=messages,
    tools=[{
        "type": "web_search_20250305",
        "name": "web_search",
        "user_location": {
            "type": "approximate",
            "city": "San Francisco",
            "region": "California",
            "country": "US",
            "timezone": "America/Los_Angeles"
        }
    }]
)
# The second response will benefit from cached search results
# while still being able to perform new searches if needed
print(f"Cache read tokens: {response2.usage.get('cache_read_input_tokens', 0)}")

Streaming

With streaming enabled, you’ll receive search events as part of the stream. There will be a pause while the search executes:

event: message_start
data: {"type": "message_start", "message": {"id": "msg_abc123", "type": "message"}}

event: content_block_start
data: {"type": "content_block_start", "index": 0, "content_block": {"type": "text", "text": ""}}

// Claude's decision to search

event: content_block_start
data: {"type": "content_block_start", "index": 1, "content_block": {"type": "server_tool_use", "id": "srvtoolu_xyz789", "name": "web_search"}}

// Search query streamed
event: content_block_delta
data: {"type": "content_block_delta", "index": 1, "delta": {"type": "input_json_delta", "partial_json": "{\"query\":\"latest quantum computing breakthroughs 2025\"}"}}

// Pause while search executes

// Search results streamed
event: content_block_start
data: {"type": "content_block_start", "index": 2, "content_block": {"type": "web_search_tool_result", "tool_use_id": "srvtoolu_xyz789", "content": [{"type": "web_search_result", "title": "Quantum Computing Breakthroughs in 2025", "url": "https://example.com"}]}}

// Claude's response with citations (omitted in this example)

Batch requests

You can include the web search tool in the Messages Batches API. Web search tool calls through the Messages Batches API are priced the same as those in regular Messages API requests.

Usage and pricing

Web search usage is charged in addition to token usage:

"usage": {
  "input_tokens": 105,
  "output_tokens": 6039,
  "cache_read_input_tokens": 7123,
  "cache_creation_input_tokens": 7345,
  "server_tool_use": {
    "web_search_requests": 1
  }
}

Web search is available on the Claude API for $10 per 1,000 searches, plus standard token costs for search-generated content. Web search results retrieved throughout a conversation are counted as input tokens, in search iterations executed during a single turn and in subsequent conversation turns. Each web search counts as one use, regardless of the number of results returned. If an error occurs during web search, the web search will not be billed.

Product Guide

Account

Help

Web search

Web search tool

Supported models

How web search works

How to use web search

Tool definition

Max uses

Domain filtering

Localization

Response

Search results

Citations

Errors

`pause_turn` stop reason

Prompt caching

Streaming

Batch requests

Usage and pricing

​Web search tool

​Supported models

​How web search works

​How to use web search

​Tool definition

​Max uses

​Domain filtering

​Localization

​Response

​Search results

​Citations

​Errors

​pause_turn stop reason

​Prompt caching

​Streaming

​Batch requests

​Usage and pricing

Web search tool

Supported models

How web search works

How to use web search

Tool definition

Max uses

Domain filtering

Localization

Response

Search results

Citations

Errors

`pause_turn` stop reason

Prompt caching

Streaming

Batch requests

Usage and pricing