Toolsify.dev

TOON Formatter

Free online JSON to TOON formatter. Convert JSON into Token-Oriented Object Notation (TOON) for more efficient and LLM-friendly data representation.

Raw JSON

TOON Output

Awaiting Input

Your TOON formatted output will appear here.

TOON for LLM Inputs

JSON to TOON Formatter for Token-Saving Prompts

TOON (Token-Oriented Object Notation) is a compact, human-readable data format that encodes your existing JSON model in a way that’s friendlier for Large Language Models.

Instead of sending verbose JSON into your prompt, TOON combines YAML-style indentation for nested objects with CSV-style tabular arrays for uniform object lists—aiming to reduce tokens while keeping the structure explicit.

Use this TOON formatter to convert JSON instantly in your browser, then copy the TOON output into your LLM workflow.

Why TOON?

  • Token-efficient structure for LLM prompts
  • Deterministic, lossless representation of JSON
  • Tabular arrays for uniform objects
  • Explicit hints like `[N]` lengths and {fields}

Key Features of a TOON Formatter

TOON is designed as a translation layer from JSON to an LLM-friendly, compact representation.

Token-Efficient Encoding

TOON aims to reduce tokens compared to formatted JSON by using minimal syntax and structure-aware representations.

Lossless JSON Model

Encode JSON data into TOON without changing the data model—intended for deterministic, lossless round-trips.

CSV-Like Tabular Arrays

Uniform arrays of objects can collapse into a table that declares fields once and streams row values line-by-line.

LLM-Friendly Guardrails

TOON adds explicit structure hints such as `[N]` array lengths and `{fields}` headers to improve parsing reliability.

How JSON Gets Converted Into TOON

TOON preserves your JSON structure while expressing it with a compact syntax that helps models follow rows, fields, and nesting.

Example: Uniform Arrays of Objects

JSON input

{
  "metrics": [
    { "date": "2025-01-01", "views": 6138, "clicks": 174 },
    { "date": "2025-01-02", "views": 4616, "clicks": 274 }
  ]
}

TOON output (shape)

metrics[2]{date,views,clicks}:
  2025-01-01,6138,174
  2025-01-02,4616,274

When TOON Is Not the Best Choice

TOON shines with tabular eligibility, but other formats can be better for complex, non-uniform JSON.

Deeply nested data

When tabular arrays can’t be formed, JSON compact or other structured representations may reduce tokens more effectively.

Non-uniform arrays

If array items have inconsistent fields, TOON’s table savings can diminish. Consider JSON when your structure varies a lot.

Privacy & Security: Local Conversion

This TOON formatter runs conversion in your browser using client-side JavaScript. Your JSON is not transmitted to a server for formatting.

That makes it a safer choice when you’re preparing prompt data, configuration, or structured content you’d rather keep local.

TOON Formatter — Frequently Asked Questions

Convert JSON to TOON for LLM-friendly, token-efficient prompts

Available Tools22