API Credit Usage

You need to login or signup to use the BuiltWith API. After logging in your actual API key will be shown here.

Important: This is not the BuiltWith MCP Server

This API is for finding other MCP servers. It searches and browses the registry of remote MCP servers that BuiltWith has discovered across the web. It is a REST API for MCP discovery, not the MCP protocol endpoint for BuiltWith's own tools.

To connect Claude or another MCP client to BuiltWith, use these connector settings:

  • Server URL: https://api.builtwith.com/mcp
  • For manual API key setup, choose No sign-in and add a request header.
  • Header name: Authorization
  • Header value: Bearer 00000000-0000-0000-0000-000000000000

Include Bearer and a space before your API key in the header value. Save the connector, then call whoami-api to check authentication without using API credits.

See https://api.builtwith.com/llms.txt for the BuiltWith MCP tool reference. The examples below are for the separate REST registry API.

Introduction

The MCP API searches and browses the BuiltWith MCP registry - the list of other remote MCP (Model Context Protocol) servers that BuiltWith has discovered across the web, published at builtwith.com/mcp-registry. This is a plain REST endpoint (JSON/XML/CSV/TXT), not an MCP protocol endpoint itself.

This is particularly useful for AI agents and MCP clients that need to discover which remote MCP servers exist for a given task - for example finding payments, CRM, or developer-tool MCP servers by keyword or category before connecting to them.

This endpoint is free of charge and does not use API credits. It is rate limited to 1 request per second per API key.

This data is also exposed as a tool via the BuiltWith MCP server (https://api.builtwith.com/mcp).

Authentication

You must provide your API key in each lookup. Our endpoints are HTTPS only, providing key encryption. Never expose your API key.

Your API Key is
00000000-0000-0000-0000-000000000000

You can supply your key as a query string parameter or as an HTTP header:

  • Query string: ?KEY=00000000-0000-0000-0000-000000000000
  • HTTP header: Authorization: API 00000000-0000-0000-0000-000000000000
Working Examples

JSON Search the registry for MCP servers matching a keyword
https://api.builtwith.com/mcp2/api.json?KEY=00000000-0000-0000-0000-000000000000&SEARCH=payments

JSON List MCP servers in a category, second page (results 101-200)
https://api.builtwith.com/mcp2/api.json?KEY=00000000-0000-0000-0000-000000000000&CATEGORY=developer-tools&OFFSET=100

JSON Search within a specific category
https://api.builtwith.com/mcp2/api.json?KEY=00000000-0000-0000-0000-000000000000&SEARCH=stripe&CATEGORY=ecommerce

XML Search the registry for MCP servers matching a keyword
https://api.builtwith.com/mcp2/api.xml?KEY=00000000-0000-0000-0000-000000000000&SEARCH=payments

CSV Search the registry for MCP servers matching a keyword
https://api.builtwith.com/mcp2/api.csv?KEY=00000000-0000-0000-0000-000000000000&SEARCH=payments

TXT Search the registry for MCP servers matching a keyword
https://api.builtwith.com/mcp2/api.txt?KEY=00000000-0000-0000-0000-000000000000&SEARCH=payments

Response

Results are records containing Domain, Category, Description, and an Endpoints array. Each endpoint contains its URL, whether authentication is required, its supported Tools (methods), and its complete Overview discovery object when available. Overview can include instructions, protocolVersion, serverInfo, capabilities, and additional fields reported by the remote MCP server. Results are sorted alphabetically by domain, up to 100 per page.

[
  {
    "Domain": "example.com",
    "Category": "Developer Tools",
    "Description": "Example MCP server description",
    "Endpoints": [
      {
        "Endpoint": "https://example.com/mcp",
        "AuthRequired": true,
        "Tools": [
          { "Name": "search_orders", "Description": "Search orders by customer or status" }
        ],
        "Overview": {
          "instructions": "Use this server to search and manage orders.",
          "protocolVersion": "2025-06-18",
          "serverInfo": { "name": "example-orders", "version": "1.0.0" },
          "capabilities": { "tools": { "listChanged": false } }
        }
      }
    ]
  }
]

CSV and TXT responses flatten Endpoints into a single column and include a separate Overview column containing the endpoint URL and its JSON overview. TXT is tab-separated with no header row.

Domain,Category,Description,Endpoints,Overview
example.com,Developer Tools,Example MCP server description,"https://example.com/mcp [search_orders, get_order]","https://example.com/mcp: {""instructions"":""Use this server to search and manage orders.""}"

SEARCH matches against the domain, description, endpoint URLs, tool names/descriptions, and overview instructions - so searching for a method name or an instruction keyword finds matching MCP servers, not just matching domains.

Pagination metadata is returned as response headers rather than in the body: X-TOTAL-COUNT (total matches), X-OFFSET (the requested offset), X-PAGE-SIZE (always 100), and X-HAS-MORE (true/false). Pass a larger OFFSET to fetch the next page.

Categories

The public categories endpoint lists every valid CATEGORY slug, its friendly label, and its current entry count. It does not require an API key or use API credits.

https://api.builtwith.com/mcp2/categories.json

XML and CSV are also available at /mcp2/categories.xml and /mcp2/categories.csv.

SlugLabelCount
ai---machine-learningAI & Machine Learning2866
analyticsAnalytics2063
api-toolsAPI Tools1611
browser-toolsBrowser Tools260
cloud-servicesCloud Services236
collaborationCollaboration315
content-toolsContent Tools2481
data-collectionData Collection1846
databasesDatabases256
designDesign439
developer-toolsDeveloper Tools2022
devopsDevOps231
ecommerceeCommerce3305
game-developmentGame Development221
general-toolsGeneral Tools6579
learning-resourcesLearning Resources1175
marketingMarketing2317
productivityProductivity2503
security---testingSecurity & Testing1098
social-mediaSocial Media547
API Reference
  • KEY (required): your BuiltWith API key.
  • SEARCH (optional): matches against the MCP server's domain, description, endpoint URLs, tool (method) names/descriptions, and overview instructions. At least one of SEARCH or CATEGORY is required.
  • CATEGORY (optional): a category slug from the categories reference. At least one of SEARCH or CATEGORY is required.
  • OFFSET (optional, default 0): pagination offset; page size is fixed at 100 results.
  • Formats: json, xml, csv, and txt.
  • Credit cost: free - this endpoint does not use API credits.
  • Rate limit: 1 request per second per API key, tighter than the general API rate limit, since this endpoint is free.
Special Domains

We maintain three lists of use for you when looking up domains: Ignore Domains, Ignore TLDs and the BuiltWith Suffix List.

Ignore List
This is our own internal list of domains we do not index. They are either blocked, contains too many misleading technologies or too many subdomains with user generated content.

Ignore TLDs
This lists the top-level domains and suffixes BuiltWith ignores when indexing websites.

BuiltWith Suffix List
This is based on the Public Suffix List but includes many additional entries for companies with subdomains that should be considered top level domains. This list provides us with better visibility for internal websites for example it brings northernbeaches.nsw.gov.au to the top level over nsw.gov.au.

Ignore Domains (XML, JSON or TXT)
https://api.builtwith.com/ignoresv1/api.json
Ignore TLDs (XML, JSON or TXT)
https://api.builtwith.com/ignoretldsv1/api.json
Suffix Domains (XML, JSON or TXT)
https://api.builtwith.com/suffixv1/api.json
Error Codes

Note error messages in this format cannot be guaranteed, your implementation should also consider non-200 response codes as errors. The Lookup property will be null (json) or not provided (xml) if the error is server related. View all potential well-formed error codes.

Terms of Use

Our standard terms cover the use all of our APIs.

In general, you can use the API to enhance your product in many ways. The only limitation is you cannot resell the data as-is or provide duplicate functionality to builtwith.com and its associated services.