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

For Example, the value "fr-CA fr en" represents a preference for French as spoken in Canada, then French (without a region designation), followed by English (without a region designation).

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

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