Zero Overhead Object Notation (ZOON)

Zero Overhead Object Notation (ZOON) is a token-optimized data format designed to maximize LLM Context Window efficiency. It removes all redundancy from your data, achieving token compression rates superior to JSON, TOON, ZON, and CSV. Written by Carsen Klock.

Why ZOON?

LLM Context Tokens cost money. Standard JSON is verbose. ZOON is optimal.

Token Benchmarks (GPT-5 Tokenizer)

Format	Tokens	Savings vs JSON
ZOON	6,274	60%
ZON	7,840	50%
TOON	8,630	45%
JSON	15,685	—

Key Features

Feature	Description
Indexed Enums	field!opt1|opt2 uses numeric indices for compact output
Header Aliasing	%a=long.prefix reduces nested redundancy
Constant Hoisting	@field=value moves repeated values to header
Auto-Increment	i+ type or +N count for implicit rows
Boolean Shorthand	1/0 (tabular) or y/n (inline)
Space Delimiters	More token-efficient than commas or pipes
Dual Format	Tabular (arrays) and Inline (objects)

ZOON vs TOON

Feature	TOON	ZOON
Delimiter	Pipes | / Commas	Spaces
Nested Data	❌ Flattened only	✅ Aliasing & Unflattening
Auto-increment	❌ Must include IDs	✅ i+ or +N
Single objects	❌ Arrays only	✅ Inline {...}
Type Safety	❌ None	✅ Header validated

Installation

bun add @zoon-format/zoon

CLI

npm install -g @zoon-format/cli
zoon input.json -o output.zoon --stats

Quick Start

import { encode, decode } from "@zoon-format/zoon";

// Arrays → Tabular format
const users = [
  { id: 1, role: "Admin", active: true },
  { id: 2, role: "User", active: true },
  { id: 3, role: "User", active: false },
];

console.log(encode(users));
// # id:i+ role=Admin|User active:b
// Admin 1
// User 1
// User 0

// Objects → Inline format
const config = {
  server: { host: "localhost", port: 3000, ssl: true },
  features: { darkMode: true, analytics: false },
};

console.log(encode(config));
// server:{host=localhost port:3000 ssl:y} features:{darkMode:y analytics:n}

Format Overview

Tabular Format (Arrays)

# id:i+ name:s role=Admin|User active:b
Alice Admin 1
Bob User 1
Carol User 0

Types:

Code	Type	Description
s	String	Spaces → _
i	Integer	Whole numbers
b	Boolean	1/0
i+	Auto-Increment	Omitted from body
a	Array	[a,b,c]

Compression:

Marker	Meaning
"	Same as row above
>	Previous + 1
~	Null

Inline Format (Objects)

server:{host=localhost port:3000 ssl:y} db:{driver=postgres port:5432}

Pattern	Type
key=val	String
key:123	Number
key:y / key:n	Boolean
key:~	Null
key:{...}	Nested Object
key:[a,b]	Array

CLI Usage

# Encode JSON to ZOON
zoon input.json -o output.zoon

# Decode ZOON to JSON
zoon data.zoon -o output.json

# Show token savings
zoon data.json --stats

Packages

Package	Description	Link
@zoon-format/zoon	Core encode/decode library	npm
@zoon-format/cli	Command-line interface	npm
zoon-format	Python bindings	PyPI
zoon-go	Go module	GitHub
zoon-format	Rust Crate	crates.io

Links

• Full Specification
• Playground

License

MIT © 2025-PRESENT Carsen Klock