FlatBuffers is a cross platform serialization library architected for
maximum memory efficiency. It allows you to directly access serialized data without parsing/unpacking it first, while still having great forwards/backwards compatibility.

Quick Start

Build the compiler for flatbuffers (flatc)

Use cmake to create the build files for your platform and then perform the compilation (Linux example).
Define your flatbuffer schema (.fbs)

Write the schema to define the data you want to serialize. See monster.fbs for an example.
Generate code for your language(s)

Use the flatc compiler to take your schema and generate language-specific code:

Which generates monster_generated.h and monster_generated.rs files.
Serialize data

Use the generated code, as well as the FlatBufferBuilder to construct your serialized buffer. (C++ example)
Transmit/store/save Buffer

Use your serialized buffer however you want. Send it to someone, save it for later, etc...
Read the data

Use the generated accessors to read the data from the serialized buffer.

It doesn't need to be the same language/schema version, FlatBuffers ensures the data is readable across languages and schema versions. See the Rust example reading the data written by C++.