I'm new with ASP, so I would love to get some help here. Also just next to the binary choice, You'll see 'Text' is clicked. After that, construct a form data body to see the file as it's being uploaded. readAsBinaryString () The readAsBinaryString method of a FileReader object asynchronously reads the file. I'm now trying to upload this file as a binary file on that API but I'm not getting how to upoad the file as a binary. There are other REST client extensions in Chrome and Firefox browsers but these extensions do not allow to test your file upload REST services. I never seen a AJAX with a