2023-05-02 2026-06-26 Specification Required Mark Nottingham, Sanjay Dalal New problem types and changes to existing ones can be requested using the registration request interface or the HTTPAPI mailing list. about:blank See HTTP Status Code N/A https://iana.org/assignments/http-problem-types#date Date Not Acceptable 400 RFC9458, Section 6.5.2 https://iana.org/assignments/http-problem-types#ohttp-key Oblivious HTTP key configuration not acceptable 400 RFC9458, Section 5.3 https://iana.org/assignments/http-problem-types#digest-unsupported-algorithms Unsupported Hashing Algorithms 400 RFC-ietf-httpapi-digest-fields-problem-types-06, Section 3.1 https://iana.org/assignments/http-problem-types#digest-invalid-values Invalid Digest Values 400 RFC-ietf-httpapi-digest-fields-problem-types-06, Section 3.2 https://iana.org/assignments/http-problem-types#digest-mismatched-values Mismatched Digest Values 400 RFC-ietf-httpapi-digest-fields-problem-types-06, Section 3.3