Custom HTTP header value - trying to pass umlaut characters

node.js express character-encoding diacritics

Summary of what was written in the other related question and in comments:

You may put any 'printable' ASCII char in your custom header value field.
If you want to use special characters, encode these characters following whatever rules/charset/encoding you choose. As long as this encoding it uses simple ASCII chars, it's OK. An example is using UTF-8 and encoding string chars to \u%%.
On the server side - you must manually make sense out of the encoded string, probably by decoding it using the rules of the character set/encoding paradigm you chose before.

CodeHunter