Why should I use FlatBuffers instead of Protocol Buffers or JSON?

Updated

Use FlatBuffers when you need to read serialized data without a parsing or unpacking step, want to avoid per-object heap allocation, and expect your schema to evolve over time. It is a strong fit for performance-critical, cross-platform systems such as games. Choose Protocol Buffers or JSON instead when you need maximum ecosystem familiarity, human-readable payloads, or very small generated code.

What FlatBuffers actually gives you

FlatBuffers is an open-source, cross-platform serialization library (Apache license v2.0, originally created at Google for game development). Its documented advantages are:

  • No parsing/unpacking step. You access serialized data directly, without unpacking or parsing it into a secondary representation first.
  • Memory efficiency and speed. The only memory needed to access your data is the buffer itself; no heap is required.
  • Backwards and forwards compatibility. The schema can evolve over time while remaining compatible with old flatbuffers.
  • Small footprint. Minimal dependencies and a small code footprint.

It supports C++, C#, C, Go, Java, Kotlin, JavaScript, Lobster, Lua, TypeScript, PHP, Python, Rust, and Swift.

How it compares with Protocol Buffers and JSON

Dimension FlatBuffers Protocol Buffers JSON
Access model Direct access to the buffer, no parse/unpack step Requires parsing/unpacking to a secondary representation Requires parsing; dynamic typing
Memory behavior Only the buffer is needed; no heap required Often coupled with per-object memory allocation Runtime inefficiency when serializing from statically typed languages
Code size Small footprint Code is an order of magnitude bigger (per the docs' comparison) —
Readability Optional text format (JSON) available — Very readable
Best fit Performance-critical, cross-platform apps — Dynamically typed languages and systems with little to no information ahead of time about what data needs to be stored

The docs are explicit that JSON remains a better choice for systems that know very little in advance about what data must be stored, and that JSON pairs well with dynamically typed languages such as JavaScript. For statically typed languages, JSON forces you to write more code to access data and adds runtime inefficiency.

A concrete way to decide

Take a task like a game client that receives position and state updates many times per second and must read a few fields from each message. With FlatBuffers, the received buffer is the data: you read fields directly with no unpacking pass and no per-object allocation. With a parse-then-access format, every message pays a conversion cost before the first field is read. If your messages are instead configuration files read once at startup, or payloads you want humans to inspect and edit, JSON's readability is likely worth more than the access speed.

Before you commit

  • Schema first. FlatBuffers is schema-driven (.fbs files compiled with flatc), so plan for a build step and a schema evolution policy; the compatibility guarantee depends on following the documented evolution rules.
  • Check your language. Confirm your target language appears in the supported list above; the docs also publish per-language guides and supported configurations.
  • Measure your case. The docs include benchmarks and a white paper; use them as background, then benchmark your own access pattern, since the benefit comes from skipping the unpacking step.

If those conditions hold, FlatBuffers is the better default; if readability or minimal tooling matters more, stay with JSON or Protocol Buffers.