If there's a JSON parser faster than a PB parser (for the same underlying data content) it just means the JSON parser was optimized more. By every rule in computing, PB parsing is far faster than JSON for every use case for a simple reason: the messages use less RAM, and therefore, moving the data into the processor and decoding it takes less time.

Theoretical performance doesn't matter in UX, only real world. Yes conceptually it's possible to make protobuffs faster than json, but someone still has to build that. Fast native json parsers already exist, that's the benchmark protobuffs has to beat significantly to make the worse DX worth it.

I believe the answer is „it depends”: https://medium.com/aspecto/protobuf-js-vs-json-stringify-per....

yes, sure it depends on the implementation, as the poster above said. You need to compare similarly optimized implementstions.. but really: no surprise?!?