Network error when using the official uploader UI

Hello oreolek, do you have some sample code for your use case? You can also try plugging in your developer token and folder ID into the sample CodePen here: https://codepen.io/box-platform/pen/QvqGwr

The first call to https://upload.box.com/api/2.0/files/content is correct since that's how the Box Upload File API works (https://developer.box.com/reference#upload-a-file). The preflight call checks whether the file you want to upload will be accepted by Box before you have to send the bytes over the wire.

Tried it on CodePen (folderId: 0). Still a network error.

Two possibilities that I can think of:

• Have you added the domains of both your app and the two needed by CodePen (https://s.codepen.io and http://s.codepen.io) to the CORS whitelisted domains in your application configuration? See: https://developer.box.com/docs/box-content-uploader#section-cross-origin-resource-sharing
• Make sure the folder ID is a string and not an integer (e.g. use '0'). The fact that we don't support integers isn't great so we'll update this to support both numbers and strings in a later release.

Added the domains to CORS and converted folder ID to string. I even changed my Internet provider to open all ports and get a white IP.

Still a network error.

That's unfortunate. Do you mind sharing a screencast of your process with the network panel open? Otherwise a screenshot of the network error with the network panel and console logs both visible works as well.

Example: