HTTP Header Checker

openapi: 3.1.0
info:
  title: HTTP Header Checker
  description: 'Sends a request to a web address you provide and reports back everything the server said in response: the
    status code, all the response headers, how many times it got redirected, and how long the whole thing took.'
  version: 1.0.0
  contact:
    name: _done
    url: https://forms.gle/5KzuSFH7p8hHtDmz7
    email: info@underscoredone.com
  x-openapi-url: https://http-header-checker.underscoredone.com/openapi.json
  x-logo:
    url: https://underscoredone.com/logo.png
    altText: _done
  x-guidance: Call this when you need to inspect what a web server returns before downloading content, such as checking caching
    rules, security headers, redirect chains, or content types. Provide a full URL with http:// or https://. Do not use this
    to scrape page content, only headers and status metadata are returned.
  x-ai-instructions: Call this when you need to inspect what a web server returns before downloading content, such as checking
    caching rules, security headers, redirect chains, or content types. Provide a full URL with http:// or https://. Do not
    use this to scrape page content, only headers and status metadata are returned.
  x-provider: _done — single-purpose utility APIs for developers and AI agents. Pay per call with USDC on Base Mainnet or
    Solana Mainnet.
  x-pricing:
    model: pay-per-call
    currency: USDC
    network: Base Mainnet or Solana Mainnet
    price: $0.01
  x-keywords:
  - network
  - http header checker
  - headers
  - url lookup
  - redirect check
  - security headers
  - cache control
  - status code
  - web debugging
  - utility
  - api
  - ai-agent
  - pay-per-call
  - usdc
  - x402
  x-category: http headers
  x-provider-url: https://underscoredone.com
  x-agentcash-auth:
    mode: paid
  x-402:
    price: $0.01
    network: eip155:8453
    asset: '0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913'
    pay_to: '0xE9740820225B3918b4ddd1292C7cA4Ca0e2C2F08'
    facilitator: https://api.cdp.coinbase.com/platform/v2/x402
    scheme: exact
    description: 'Sends a request to a web address you provide and reports back everything the server said in response: the
      status code, all the response headers, how many times it got redirected, and how long the whole thing took.'
    mime_type: application/json
    networks:
    - network: eip155:8453
      asset: '0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913'
      pay_to: '0xE9740820225B3918b4ddd1292C7cA4Ca0e2C2F08'
    - network: solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp
      asset: EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v
      pay_to: 8ugAWAXDB8V18kiUrGZTq1oMvU3C6Fxs8hfC6rvzQT3b
paths:
  /check:
    post:
      tags:
      - http headers
      - response headers
      - headers
      - inspect http headers
      - server headers
      - header checker
      - redirect chain
      - security headers
      - http response
      - response time
      - check headers
      - ttfb
      - header inspection
      summary: Look up the response headers and status of any URL
      description: Checks a web address and reports back its status, headers, redirect path, and timing.
      operationId: handler_check_post
      requestBody:
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/Request'
        required: true
      responses:
        '200':
          description: Successful response
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Response'
              examples:
                success:
                  summary: Successful response
                  value:
                    api_version: 1.0.0
                    url: https://example.com
                    final_url: https://example.com/
                    status_code: 200
                    redirect_chain:
                    - url: http://example.com
                      status_code: 301
                    headers:
                      content-type: text/html; charset=UTF-8
                      server: nginx
                      cache-control: max-age=600
                      content-length: '1256'
                    missing_security_headers:
                    - strict-transport-security
                    - content-security-policy
                    response_time_ms: 214
        '422':
          description: Unprocessable — a required field is missing or the wrong type. Check the detail field for specifics.
          content:
            application/json:
              schema:
                type: object
                properties:
                  detail:
                    type: array
        '402':
          description: Payment required. Send a signed USDC payment on Base Mainnet or Solana Mainnet using the x402 protocol.
          headers:
            X-Payment-Response:
              description: x402 payment challenge — base64-encoded JSON with payment details.
              schema:
                type: string
        '400':
          description: Bad request — your input failed validation or could not be processed. Check the detail field for specifics.
          content:
            application/json:
              schema:
                type: object
                properties:
                  detail:
                    type: string
      x-ai-instructions: Call this when you need to inspect what a web server returns before downloading content, such as
        checking caching rules, security headers, redirect chains, or content types. Provide a full URL with http:// or https://.
        Do not use this to scrape page content, only headers and status metadata are returned.
      x-guidance: Call this when you need to inspect what a web server returns before downloading content, such as checking
        caching rules, security headers, redirect chains, or content types. Provide a full URL with http:// or https://. Do
        not use this to scrape page content, only headers and status metadata are returned.
      x-payment-info:
        price:
          fixed:
            mode: fixed
            currency: USD
            amount: '0.01'
        protocols:
        - x402: {}
components:
  schemas:
    HTTPValidationError:
      properties:
        detail:
          items:
            $ref: '#/components/schemas/ValidationError'
          type: array
          title: Detail
      type: object
      title: HTTPValidationError
    RedirectHop:
      properties:
        url:
          type: string
          title: Url
          description: The address that redirected onward
        status_code:
          type: integer
          title: Status Code
          description: The status number the server gave at this step
      type: object
      required:
      - url
      - status_code
      title: RedirectHop
      example:
        status_code: 301
        url: http://example.com
    Request:
      properties:
        url:
          type: string
          title: Url
          description: The full web address to check, including http:// or https://
        method:
          anyOf:
          - type: string
          - type: 'null'
          title: Method
          description: Either GET or HEAD. GET fetches the page normally, HEAD only asks for headers without the body.
          default: GET
        follow_redirects:
          anyOf:
          - type: boolean
          - type: 'null'
          title: Follow Redirects
          description: Whether to follow redirects to their final destination or stop at the first one.
          default: true
      type: object
      required:
      - url
      title: Request
      example:
        follow_redirects: true
        method: GET
        url: https://example.com
    Response:
      properties:
        api_version:
          type: string
          title: Api Version
          description: The version number of this service
          default: 1.0.0
        url:
          type: string
          title: Url
          description: The web address that was requested
        final_url:
          type: string
          title: Final Url
          description: The web address the check actually ended up at, after any redirects
        status_code:
          type: integer
          title: Status Code
          description: The status number the web server sent back
        redirect_chain:
          items:
            $ref: '#/components/schemas/RedirectHop'
          type: array
          title: Redirect Chain
          description: Each step the check was redirected through, if any
        headers:
          additionalProperties:
            type: string
          type: object
          title: Headers
          description: All the information the web server sent back about the page
        missing_security_headers:
          items:
            type: string
          type: array
          title: Missing Security Headers
          description: Common protective settings that the web server did not include
        response_time_ms:
          type: number
          title: Response Time Ms
          description: How long the check took, in thousandths of a second
      type: object
      required:
      - url
      - final_url
      - status_code
      - redirect_chain
      - headers
      - missing_security_headers
      - response_time_ms
      title: Response
      example:
        api_version: 1.0.0
        final_url: https://example.com/
        headers:
          content-type: text/html; charset=UTF-8
          server: nginx
        missing_security_headers:
        - content-security-policy
        - strict-transport-security
        redirect_chain:
        - status_code: 301
          url: http://example.com
        response_time_ms: 214.0
        status_code: 200
        url: https://example.com
    ValidationError:
      properties:
        loc:
          items:
            anyOf:
            - type: string
            - type: integer
          type: array
          title: Location
        msg:
          type: string
          title: Message
        type:
          type: string
          title: Error Type
        input:
          title: Input
        ctx:
          type: object
          title: Context
      type: object
      required:
      - loc
      - msg
      - type
      title: ValidationError
  securitySchemes:
    siwx:
      type: apiKey
      in: header
      name: SIGN-IN-WITH-X
      description: CAIP-122 wallet signature for repeat access after payment
servers:
- url: https://http-header-checker.underscoredone.com
  description: Production
tags:
- name: http headers
- name: response headers
- name: headers
- name: inspect http headers
- name: server headers
- name: header checker
- name: redirect chain
- name: security headers
- name: http response
- name: response time
- name: check headers
- name: ttfb
- name: header inspection
x402Version: 2
x-payment-accepts:
- scheme: exact
  network: eip155:8453
  payTo: '0xE9740820225B3918b4ddd1292C7cA4Ca0e2C2F08'
  asset: '0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913'
- scheme: exact
  network: solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp
  payTo: 8ugAWAXDB8V18kiUrGZTq1oMvU3C6Fxs8hfC6rvzQT3b
  asset: EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v