Claims_locales is an OPTIONAL OAuth Parameters Registry entry used in OpenID Connect to indicate the End-User's preferred languages and scripts for Claims being returned, represented as a space-separated list of BCP 47 (RFC 5646) Language-Tag values, ordered by preference.

An error SHOULD NOT result if some or all of the requested locales are not supported by the OpenID Connect Provider.

When the OP determines, either through the Claims_locales Parameter, or by other means, that the Resource Owner and OAuth Client are requesting Claims in only one set of languages and scripts, it is RECOMMENDED that OpenID Connect Providers return Claims without Language-Tags when they employ this language and script.
It is also RECOMMENDED that OAuth Clients be written in a manner that they can handle and utilize Claims using Language-Tags.

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