CORS Headers Generator
Configure your cross-origin policy once and get consistent, correct config for raw HTTP headers, nginx, Express, and FastAPI. Everything runs in your browser — nothing is uploaded.
About this tool
CORS misconfiguration is one of the most common reasons an API "works in Postman but fails in the browser". This generator takes one policy — origins, methods, headers, credentials, preflight cache — and emits it in four equivalent forms: the raw response headers (split into preflight and actual response, since browsers read different headers from each), an nginx location block with proper OPTIONS handling, the Express cors() options object, and FastAPI's CORSMiddleware. It also enforces the rule browsers enforce: a wildcard origin cannot be combined with credentials.
Your configuration never leaves the page — there is no server, no upload, and no tracking of tool inputs.