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CORS Tester

Send an authorized server-side request with a simulated Origin, method, request-header names, and credential mode, then interpret preflight and Access-Control-Allow-* responses.

CORS Tester

Send a request from any origin and see exactly which Access-Control-Allow-* headers an API returns — and whether a browser would allow the response.

The website that would call the API, e.g. https://app.example.com.

Comma-separated header names your app sends. Non-simple ones (Authorization, Content-Type) trigger a preflight.

Cookies or Authorization sent with the request (fetch credentials: 'include').

Try an example:

The request runs through the AppKiro server so response headers can be inspected. Do not include secrets; retention and logging guarantees are not asserted here.

What is CORS Tester?

Send an authorized server-side request with a simulated Origin, method, request-header names, and credential mode, then interpret preflight and Access-Control-Allow-* responses. An authorized HTTP(S) endpoint, Origin, method, requested header names, and credential simulation settings. Actual response status and relevant CORS headers, plus a preflight OPTIONS result when the selected request requires one.

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What the tool does

  • Input: An authorized HTTP(S) endpoint, Origin, method, requested header names, and credential simulation settings.
  • Controls and processing: Origin, method, Access-Control-Request-Headers simulation, credentials, timeout, and interpretation of Access-Control-Allow-Origin/Methods/Headers/Credentials.
  • Output: Actual response status and relevant CORS headers, plus a preflight OPTIONS result when the selected request requires one.

How to use it

  1. Provide the input. An authorized HTTP(S) endpoint, Origin, method, requested header names, and credential simulation settings.
  2. Review the settings. Origin, method, Access-Control-Request-Headers simulation, credentials, timeout, and interpretation of Access-Control-Allow-Origin/Methods/Headers/Credentials.
  3. Generate, inspect, and export. Actual response status and relevant CORS headers, plus a preflight OPTIONS result when the selected request requires one.

Key features

  • Input: An authorized HTTP(S) endpoint, Origin, method, requested header names, and credential simulation settings.
  • Controls and processing: Origin, method, Access-Control-Request-Headers simulation, credentials, timeout, and interpretation of Access-Control-Allow-Origin/Methods/Headers/Credentials.
  • Output: Actual response status and relevant CORS headers, plus a preflight OPTIONS result when the selected request requires one.

Useful workflows

  • Send an authorized server-side request with a simulated Origin, method, request-header names, and credential mode, then interpret preflight and Access-Control-Allow-* responses.
  • Use it when you need this deliverable or diagnostic result: Actual response status and relevant CORS headers, plus a preflight OPTIONS result when the selected request requires one.
  • Place it before the next verified workflow step: reproducing the request in the actual browser application and checking DevTools.

Limits and safety notes

  • A server-side test does not perfectly reproduce every browser security context, cache, service worker, redirect, cookie, client certificate, or private-network restriction.

Troubleshooting

  • Use only an authorized public target; confirm the scheme, host, port, DNS/TLS, timeout, and temporary least-privilege credentials before retrying.
  • Compare the result with target-side logs and an appropriate browser or CLI client; a timeout or server-side response alone does not prove the application configuration is correct.
  • A server-side test does not perfectly reproduce every browser security context, cache, service worker, redirect, cookie, client certificate, or private-network restriction.

Frequently asked questions

What is CORS Tester?

Send an authorized server-side request with a simulated Origin, method, request-header names, and credential mode, then interpret preflight and Access-Control-Allow-* responses.

How do I use CORS Tester?

Provide the expected input, review the page settings, then verify the result before copying or downloading it. Expected output: Actual response status and relevant CORS headers, plus a preflight OPTIONS result when the selected request requires one.

What input does it accept?

An authorized HTTP(S) endpoint, Origin, method, requested header names, and credential simulation settings.

What output does it produce?

Actual response status and relevant CORS headers, plus a preflight OPTIONS result when the selected request requires one.

What are the limits?

A server-side test does not perfectly reproduce every browser security context, cache, service worker, redirect, cookie, client certificate, or private-network restriction.

Related AppKiro tools

cURL Command ParserUse it for the adjacent next task: Parse a cURL command as text to inspect method, URL, headers, cookies, query parameters, body, authentication, flags, and warnings without executing the request.Database Connection CheckerUse it for the adjacent next task: Test authorized public PostgreSQL, MySQL/MariaDB, MongoDB, or Redis endpoints through a server-side connection and inspect limited read-only metadata when permitted.WebSocket TesterUse it for the adjacent next task: Open a browser WebSocket connection to an authorized ws:// or wss:// endpoint, send text, JSON, or binary messages, and inspect received data and connection logs.

Start with a verified input

Use an authorized non-production target and temporary or redacted data. Compare the result with target-side logs before acting on it.

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