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I know it's the official reason, but it's also a really bad one - nothing prevents current JSON parsers to add some weird syntactic rules inside plain strings (

I know it's the official reason, but it's also a really bad one - nothing prevents current JSON parsers to add some weird syntactic rules inside plain strings (similar to "use strict" in JS), but you don't see that happen. It's always been a completely hypothetical issue. The only real reason why comments would be problematic is that they are a pain to preserve in a consistent way when editing a file, and thus would require extra work in parsers / serializers. Still, it would be worth the cost imo.

HelloNurse 6y ago
In most applications reading and writing JSON are completely separate operations and roundtripping comments makes no sense. Actual JSON-reading applications must ignore comments because they aren't allowed to care about them. On the other hand anything useful can be placed in a proper field, a comment would be a hack to pass information to human readers but not to JSON consumers (saving some time and memory). Such a technique could only be considered if people are supposed to read the JSON files and some information is useful for them but not for the reading application: a niche within a niche. Preserving comments would actually be a complicated special purpose feature, reserved for something like structured text editors that can perform nonstandard parsing with comments included in their special object model (of the large Javascript subset/superset/variant they choose to support and roundtrip, not of JSON).
sneak 6y ago
I agree that it was stupid. I am 100% pro-comment.