10 Feb 2020   react

ReactNative on Android requires a mime type when uploading files with FormData. But the only way to get the mime type of a user-chosen file is to read the file or files into memory after a user select one or more. In all of my use cases, my server didnā€™t care if the mimetype was in the FormData.

The easy solution is to just set the mimetype to a binary file type (e.g. application/octet-stream):

let data = new FormData();
data.append("file", {
  name: "cool.pdf",
  uri: "///files/cool.pdf",
  // MIME-type required on Android
  type: "application/octet-stream"

fetch("http://example.com/upload-file", data);