# HTTP 415 Unsupported Media Type

Encountered an error in IE11 a while ago using the [Swagger UI](http://swagger.io/swagger-ui/), on a DELETE REST request, which returned “HTTP 415 Unsupported Media Type” error, while Firefox/Chrome had no problem with the same request (I know, what else is new, right?). I couldn't find anything specific around Swagger and HTTP 415.  
As it turns out, Swagger gets its payload data using `var data = this._formData || this._data;` in `Request.prototype.end`, but on a DELETE there is no data, so “data” is undefined. Later on it does its XHR request `xhr.send(data);`.  
No problem in Firefox/Chrome, but IE11 sends back the string `"undefined"` as `data`, and the server isn't expecting anything like that, hence the “HTTP 415 Unsupported Media Type” response.  
Explicitly setting the data to null `var data = this._formData || this._data || null;` in the Swagger UI JavaScript fixed it (or not sending the `data` when it's undefined in the xhr would work around it too). Though it rather looks like an IE bug, no?