What is TOON and how is it different from JSON?

TOON (Token-Oriented Object Notation) encodes the same data as JSON but avoids repeating keys and punctuation, so it uses fewer tokens. The conversion is lossless — you can turn TOON back into the exact JSON it came from.

How many tokens does TOON actually save?

It depends on the data. Structured, repetitive payloads like arrays of similar objects benefit most, often in the 30–60% range, because the keys are written once instead of per record. Less repetitive data saves less.

Is converting JSON to TOON and back lossless?

Yes — TOON is designed as a faithful reencoding of JSON, so a JSON → TOON → JSON round trip returns equivalent data.

When should I use TOON over plain JSON?

Use it when you're paying per token — sending structured data into an LLM prompt is the main case. For storage or APIs where tooling expects JSON, keep JSON and convert only at the model boundary.

Does my data leave the browser?

No. Conversion is fully client-side, so your payloads are never uploaded.

JSON ⇄ TOON Converter

Convert between JSON and TOON (Token-Oriented Object Notation) format. TOON reduces LLM token usage by 30-60% for structured data while maintaining readability.

Conversion Mode

Switch between JSON to TOON or TOON to JSON conversion

JSON Input

Options

Delimiter

Tab delimiter often saves more tokens

Indentation

Show length markers (#)

TOON Output

JSON TOKENS

TOON TOKENS

SAVED

About TOON Format

TOON (Token-Oriented Object Notation) is a compact, human-readable format designed for LLM prompts. It achieves 30-60% token savings compared to JSON while maintaining structure and readability.

Token Efficient: Removes redundant punctuation and declares array structures once
LLM-Friendly: Explicit lengths and fields enable better validation
Tabular Arrays: Perfect for uniform data structures like user lists or analytics
Indentation-Based: YAML-like structure with minimal syntax

About JSON ⇄ TOON Converter

Sending JSON to a language model is expensive in tokens. Every object repeats its keys, and every bracket, quote, and comma counts. TOON (Token-Oriented Object Notation) keeps the same data but lays it out so that repeated structure is written once, which is why it can substantially cut the token count of structured payloads while staying readable to a human reviewing the prompt.

This converter goes both ways. Paste JSON to get TOON you can drop into a prompt, or paste TOON to recover the original JSON your application expects. Because the round trip is lossless, you can store or transmit data as compact TOON and convert back to JSON at the boundary where your code needs it.

It runs in your browser, so nothing you paste is uploaded. That makes it safe for real request and response payloads, including ones with data you'd rather not send to a third-party service just to reformat it.

How to use JSON ⇄ TOON Converter

Pick a direction
Decide whether you're going JSON to TOON (to shrink a prompt) or TOON back to JSON (to feed your application).
Paste your input
Drop a JSON object or array, or a TOON document, into the input. A valid document converts; malformed input is reported so you can fix it.
Review the converted output
Read the result to confirm the structure survived the round trip — especially nested objects and arrays.
Copy it where you need it
Use the TOON in your LLM prompt to save tokens, or paste the JSON into your code or API request.

Frequently asked questions

CSV/JSON → TONL Converter

Convert CSV or JSON into TONL (Token-Optimized Notation Language) for compact, LLM-friendly structured data.

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Format, minify, sort keys, and validate JSON/JSONC/JSON5 with optional JSON Schema validation. Supports comments and trailing commas.

JSON to TypeScript Converter

Instantly convert JSON objects or arrays into clean TypeScript interfaces or type aliases.