CORS Header Generator — Cross-Origin Config Tool
Build CORS configuration headers interactively for web servers and APIs. Set allowed origins, methods, request headers, credentials, and preflight cache duration — then copy the generated Access-Control headers or ready-to-paste code snippets for nginx, Express.js, Flask, and .NET.
How to Use CORS Header Generator — Cross-Origin Config Tool
How to Use the CORS Header Generator
Step 1: Choose a Preset (optional)
Click one of the three preset buttons at the top of the configuration panel to instantly load a common CORS setup:
- Open API — allows all origins (
*) with GET/POST/OPTIONS and no credentials. Use for fully public APIs. - SPA + API — a single origin with full CRUD methods, Authorization header, and credentials enabled. The most common setup for a single-page app calling a backend API.
- Strict — one origin, GET only, minimal headers. Use for read-only, tightly controlled APIs.
Step 2: Configure Your CORS Policy
Allowed Origins
Enter a single origin URL (e.g., https://app.example.com), * to allow any origin, or a comma-separated list for multiple specific origins. Note: using * with credentials enabled is not permitted by browsers.
Allowed Methods Click the HTTP method buttons to toggle them on or off. Highlight the methods your API actually uses. Always include OPTIONS for preflight requests.
Allowed Headers
Toggle the common request headers your API expects to receive. Add any custom headers (e.g., X-Tenant-Id) in the text input below the toggles.
Exposed Headers (optional)
List response headers that the browser should expose to client-side JavaScript (e.g., X-Request-Id, X-Rate-Limit-Remaining).
Allow Credentials
Enable this if your API uses cookies, HTTP authentication, or TLS client certificates. Must be used with a specific origin — not *.
Max Age Sets how long (in seconds) browsers may cache preflight results. Use the quick presets (1h, 24h, 7d) or enter a custom value.
Step 3: Choose an Output Tab
Click the output tabs to switch between:
- HTTP Headers — the raw
Access-Control-*header lines to add to any HTTP response - nginx —
add_headerdirectives and preflight handler block - Express.js —
corsnpm package configuration object - Flask —
flask-corsCORS configuration - .NET —
AddCorsandUseCorsmiddleware setup for ASP.NET Core
Step 4: Copy and Apply
Click Copy to copy the output to your clipboard, then paste it into your server configuration or application code.
Frequently Asked Questions
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