I was interested to note that the Dropbox API offers a hack to avoid the extra CORS request - among other details, their server accepts this: - Set the Content

I was interested to note that the Dropbox API offers a hack to avoid the extra CORS request - among other details, their server accepts this: - Set the Content-Type to "text/plain; charset=dropbox-cors-hack" instead of "application/json" or "application/octet-stream". [0] ...which is allowed in a "Simple" request that doesn't require a separate round trip for OPTIONS. [0] - https://www.dropbox.com/developers/documentation/http/documentation https://www.dropbox.com/developers/documentation/http/docume...