Comparing against other serialization solutions, running on Windows 7 64bit. We use the LITE runtime for Protocol Buffers (less code / lower overhead), and Rapid JSON, one of the fastest C++ JSON parsers around.

We compare against Flatbuffers with the binary wire format (as intended), and also with JSON as the wire format with the optional JSON parser (which, using a schema, parses JSON into a binary buffer that can then be accessed as before).

The benchmark object is a set of about 10 objects containing an array, 4 strings, and a large variety of int/float scalar values of all sizes, meant to be representative of game data, e.g. a scene format.

Some other serialization systems we compared against but did not benchmark (yet), in rough order of applicability:

• Cap'n'Proto promises to reduce Protocol Buffers much like FlatBuffers does, though with a more complicated binary encoding and less flexibility (no optional fields to allow deprecating fields or serializing with missing fields for which defaults exist). It currently also isn't fully cross-platform portable (lack of VS support).
• msgpack: has very minimal forwards/backwards compatability support when used with the typed C++ interface. Also lacks VS2010 support.
• Thrift: very similar to Protocol Buffers, but appears to be less efficient, and have more dependencies.
• XML: typically even slower than JSON, but has the advantage that it can be parsed with a schema to reduce error-checking boilerplate code.
• YAML: a superset of JSON and otherwise very similar. Used by e.g. Unity.
• C# comes with built-in serialization functionality, as used by Unity also. Being tied to the language, and having no automatic versioning support limits its applicability.
• Project Anarchy (the free mobile engine by Havok) comes with a serialization system, that however does no automatic versioning (have to code around new fields manually), is very much tied to the rest of the engine, and works without a schema to generate code (tied to your C++ class definition).