- 🇨🇳China skyredwang Shanghai
Just to provide another reference:
BCP 47: 2.1.1. Formatting of Language Tags
At all times, language tags and their subtags, including private use
and extensions, are to be treated as case insensitive: there exist
conventions for the capitalization of some of the subtags, but these
MUST NOT be taken to carry meaning.Thus, the tag "mn-Cyrl-MN" is not distinct from "MN-cYRL-mn" or "mN-
cYrL-Mn" (or any other combination), and each of these variationsPhillips & Davis Best Current Practice [Page 6]
RFC 5646 Language Tags September 2009
conveys the same meaning: Mongolian written in the Cyrillic script as
used in Mongolia.The ABNF syntax also does not distinguish between upper- and
lowercase: the uppercase US-ASCII letters in the range 'A' through
'Z' are always considered equivalent and mapped directly to their US-
ASCII lowercase equivalents in the range 'a' through 'z'. So the tag
"I-AMI" is considered equivalent to that value "i-ami" in the
'irregular' production.Although case distinctions do not carry meaning in language tags,
consistent formatting and presentation of language tags will aid
users. The format of subtags in the registry is RECOMMENDED as the
form to use in language tags. This format generally corresponds to
the common conventions for the various ISO standards from which the
subtags are derived. ---- https://www.rfc-editor.org/rfc/rfc5646.html#section-2.1.1