In two recent Python 3 porting projects, a key incompatibility I encountered was that "json.loads(data)" on UTF-8 encoded bytes required an explicit decoding step under Python 3, rather than implicitly decoding the data as UTF-8.

Unlike many other wire formats, assuming UTF-8 for binary JSON data is a pretty safe assumption, and there's no type ambiguity here since the output type is still a properly decoded JSON object.

(This RFE has been split out from the larger RFE at #19837, which also covers implicit *encoding* to UTF-8, which is a more questionable idea)