This library implements MessagePack spec v4 with some extensions compatible with msgpack-js. It does not implement spec v5. If you need support for spec v5 (including STR8, BIN types, etc), see alternatives. This is yet another implementation of MessagePack for LuaJIT. However, unlike luajit-msgpack, luajit-msgpack-pure does not depend on the MessagePack C library. Everything is re-implemented in LuaJIT code (using the FFI but only to manipulate data structures).