Comment by mpyne

For "I need this Python dict to exist in this unrelated JavaScript program's context space" JSON is absolutely much better. If only because you completely sidestep all the various XML foibles, including its very real security foibles.

JSON is so good at this that, like CSV, it does displace better tech for that use case, but the better tech isn't usually XML but rather things like Avro or Protobuf.

For the most part people don't add on XML features to JSON. Comments are a frequent addition, sometimes schemas, but for the most part the attraction of JSON is avoiding features of XML, like external entity validation, namespaces, getting to choose between SAX or DOM styles, or being required to support unrelated XML systems just to use another.

Again, there are problem domains where those are helpful, and XML is a good fit for those. But those problem spaces end up being much smaller in scale than the ones solved by JSON, Avro, Iceberg, etc.

But the whole point to JSON is to be nearly as dumb simple as possible so that the complexity of the problem domain will necessarily be handled in a real programming language, not by the data magically trying to transform itself.