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CORS Header Generator

Generate correct CORS headers — Access-Control-Allow-Origin, methods, headers, credentials. Fix preflight failures with exact syntax — local generation, free, no signup.

100% Local Browser Native

How to Use the CORS Header Generator

1. Enter origin and needs

Allowed origins, methods, headers, credentials.

2. Generate headers

Exact syntax for server config or middleware.

3. Paste into server

Nginx, Express, or cloud config; test preflight.

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Frequently Asked Questions

Why is my fetch blocked by CORS?

The server lacks Access-Control-Allow-Origin for your origin, or preflight (OPTIONS) fails on methods/headers. Generate the exact header set and compare against live response headers.

Wildcard vs specific origin?

Wildcard (*) is simple but forbids credentials; specific origins pair with Allow-Credentials for cookies. Authenticated APIs need the specific form.

Preflight caching?

Access-Control-Max-Age caches preflights (86400s typical) to cut OPTIONS chatter. Set it once the policy stabilizes.

Do CORS configs upload?

No — generation runs locally in your browser. Nothing leaves your device.

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Last updated October 2026