The Accept-Charset header field has the following syntax:

Accept-Charset = 1#(charset [weight]) / ("*" [weight])

The user agent may provide a list of Acceptable Character Sets in the Accept-Charset header field of the request. Its value is a comma-separated list of one or more charsets and/or the wildcard value ("*").

The values of the Accept-Charset header field values are prioritized by their weight parameter.

If no wildcard ("*") is present, then any character sets not explicitly mentioned in the header field are considered "not acceptable" to the client.

A request without an Accept-Charset header field implies that the user agent will accept any charset in response.

If the media type defines a "charset" parameter, it should be included with the media type in the Accept header field, rather than in the Accept-Charset header field.

If this header field has a value that is not a valid or supported character set, the origin server shall return a 400 (Bad Request) response and may include a payload containing an appropriate Status Report. See Section 8.6.3.

Any Accept-Charset header field values that are not valid or not supported shall be ignored.