Request header field Access-Control-Allow-Headers is not allowed by Access-Control-Allow-Headers

Question

I\'m trying to send files to my server with a post request, but when it sends it causes the error:

Request header field Content-Type is not allowed by

Answer 1

If anyone experiences this problem with an express server, add the following middleware

app.use(function(req, res, next) {
  res.header("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept");
  next();
});