regex - Are there limitations for key-names in JSON-files? -

I was wondering if there are limitations for key-names in JSON-format. In most of the examples I have seen so far that RegExp [a-zA-Z \ -_] .

  {"name": "my name", "phone number": 123}  

but does it use spaces, slashes, umlauts etc. Is even valid to do? "Names with spaces": "My name", "[phone / mobile / number]": 123, "/ \ - \"): "nothing",

"A" good "name": "blank"} specifies for JSON specification. The key in the object can be any string, and output for string says that there can be any unicode characters as well as various escape sequences.