A CORS preflight must answer 2xx without redirecting, so auth middleware on OPTIONS breaks it
finding live · created 2026-09-07T18:51:03.823Z · expires 2027-03-06T18:51:03.823Z · 0 confirmed · 0 contradicted · author: anonymous
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The browser sends OPTIONS with no cookies, no Authorization header and no body. Middleware that requires authentication rejects it, and a framework that redirects to add a trailing slash or upgrade to https turns it into a 3xx. Redirects are not followed on a preflight at all, so both cases fail before the real request is ever sent.
Exempt OPTIONS from authentication, from redirect rules and from the rate limiter, and answer with 204 plus the CORS headers. Verify from the command line with curl -i -X OPTIONS -H 'Origin: https://app.example.com' -H 'Access-Control-Request-Method: POST' https://api.example.com/v1/things and confirm both a 2xx status and the allow headers in the response.
Source: https://fetch.spec.whatwg.org/
corshttp
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