[character-encoding] What does "Content-type: application/json; charset=utf-8" really mean?

When I make a POST request with a JSON body to my REST service I include Content-type: application/json; charset=utf-8 in the message header. Without this header, I get an error from the service. I can also successfully use Content-type: application/json without the ;charset=utf-8 portion.

What exactly does charset=utf-8 do ? I know it specifies the character encoding but the service works fine without it. Does this encoding limit the characters that can be in the message body?

This question is related to character-encoding mime-types

The answer is


Note that IETF RFC4627 has been superseded by IETF RFC7158. In section [8.1] it retracts the text cited by @Drew earlier by saying:

Implementations MUST NOT add a byte order mark to the beginning of a JSON text.

I exactly agree with @deceze but I want to develop this "I get an error from the service" part of the question,

We getting this kind of errors as http 415

Http 415 Unsupported Media type error

The HTTP 415 Unsupported Media Type client error response code indicates that the server refuses to accept the request because the payload format is in an unsupported format.

The format problem might be due to the request's indicated Content-Type or Content-Encoding, or as a result of inspecting the data directly.

In other words, such is seen in this example.

  • We have to set the correct content type and we have to accept the right content type as seen Add Content-Type: application/json and Accept: application/json. Otherwise, it will assume the default

To substantiate @deceze's claim that the default JSON encoding is UTF-8...

From IETF RFC4627:

JSON text SHALL be encoded in Unicode. The default encoding is UTF-8.

Since the first two characters of a JSON text will always be ASCII characters [RFC0020], it is possible to determine whether an octet stream is UTF-8, UTF-16 (BE or LE), or UTF-32 (BE or LE) by looking at the pattern of nulls in the first four octets.

      00 00 00 xx  UTF-32BE
      00 xx 00 xx  UTF-16BE
      xx 00 00 00  UTF-32LE
      xx 00 xx 00  UTF-16LE
      xx xx xx xx  UTF-8

I was using HttpClient and getting back response header with content-type of application/json, I lost characters such as foreign languages or symbol that used unicode since HttpClient is default to ISO-8859-1. So, be explicit as possible as mentioned by @WesternGun to avoid any possible problem.

There is no way handle that due to server doesn't handle requested-header charset (method.setRequestHeader("accept-charset", "UTF-8");) for me and I had to retrieve response data as draw bytes and convert it into String using UTF-8. So, it is recommended to be explicit and avoid assumption of default value.


Dart http's implementation process the bytes thanks to that "charset=utf-8", so i'm sure several implementations out there supports this, to avoid the "latin-1" fallback charset when reading the bytes from the response. In my case, I totally lose format on the response body string, so I have to do the bytes encoding manually to utf8, or add that header "inner" parameter on my server's API response.