Another vote for CBOR. I had actually designed my own binary JSON encoding out of frustration with BSON (which nobody should use IMO). My format was focused on

Another vote for CBOR. I had actually designed my own binary JSON encoding out of frustration with BSON (which nobody should use IMO). My format was focused on compactness, but I dropped it when I found CBOR which was very similar and even slightly better in places. One notably thing about CBOR is the support for both Indefinite and Definite-Length Arrays and Maps (typically streaming generators need the former whereas parsing the latter can be more efficient).