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Content-type: application/json; charset=utf-8
or
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
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What does "Content-type: application/json; charset=utf-8" really mean?