Unable to translate bytes [FC] at index 35 from specified code page to Unicode

Although the Content-Type is charset UTF-8 the received byte code FC denotes the extended ASCII character 252 which represents the umlaut "ü".

In a UTF-8 encoding the umlaut "ü" consists of two bytes. So there is a mismatch between the given encoding header and the transmitted data. So you have to check the code which generates the request.

You are sending your string encoded in utf-16, but telling (in the Content-Type header's charset) it is utf-8.

The bytes for tersü in utf-8 are:

74,65,72,73,C3,BC

However tersü (in utf-16) contains the bytes (notice the FC there):

74,0,65,0,72,0,73,0,FC,0

(Check it in this fiddle)

So it just can't understand it. So either convert your string to utf-8 in your client before sending it, or set the Content-Type charset to utf-16 .