SHOULD is defined in RFC 2119 as 3. SHOULD This word, or the adjective "RECOMMENDED", mean that there may exist valid reasons in particular circum

SHOULD is defined in RFC 2119 as 3. SHOULD This word, or the adjective "RECOMMENDED", mean that there may exist valid reasons in particular circumstances to ignore a particular item, but the full implications must be understood and carefully weighed before choosing a different course. The consequences are undefined, I feel, for a reason. You can't put them all down on paper, it depends on what all the parsers do. The parsers can accept or reject things with duplicate keys, or they can play a nice little ditty through the speakers. All it means is a parser isn't required to reject JSON with multiple keys. It can, however, do whatever the fuck it wants with them. If the wording was precise, then it should be a MUST. SHOULD indicates a terrible world of unknown consequences.