CORS

Cross-Origin Resource Sharing (CORS)

By default, requests are blocked if not same origin

SERVER must be configured to return the resource with the Access-Control-Allow-Origin: * or the specific domain you wish to allow

All non idempotent(besides GET and some POSTS with specific meme) will be first fetched with an OPTIONS

Express => https://expressjs.com/en/resources/middleware/cors.html

Flask => https://flask-cors.readthedocs.io/en/latest/#using-json-with-cors

Sometimes you can get CORS errors because of having/not having a trailing slash (something about redirects not being allowed idk)