preflight request is 308 Permanent Redirect

Access to fetch at 'http://localhost:5000/api/web/create' from origin 'http://localhost:3000' has been blocked by CORS policy: Response to preflight request doesn't pass access control check: Redirect is not allowed for a preflight request.

Origin-to-Origin Resource Sharing (CORS) - HTTP | MDN

Preflight request - MDN Web Docs Glossary: Definition of web-related terms | MDN

The browser precedes the request with the OPTIONS method.

The server is returning a 308 Permanent Redirect for the request and is therefore not considered CORSable.

cause

Server side

@app.route('/api/web/create/', methods=["GET"])

client-side

fetch(APIROOT + "web/create", {...})

So this is redirecting access without the trailing slash to a URL with one.

solution

fetch(APIROOT + "web/create/", {...}) I just did and it solved the problem.

CORS

Flask-CORS

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