JSON to TOON Converter

What is JSON to TOON Converter?

A tool for converting JSON format data to TOON (Token-Oriented Object Notation) format.

TOON is a newly emerged data format in 2025, optimized for LLM (Large Language Model) prompts. It can express the same information with 30-60% fewer tokens compared to standard JSON, significantly reducing token usage when sending large datasets to chat AIs like ChatGPT, Claude, and Gemini.

Convert your JSON input in real-time, customize delimiters, indent width, and key folding options to match your use case. Copy the results with one click and paste them directly into your LLM prompts.

Benefits of Using TOON

Reduce Token Costs - Potential to reduce API usage fees by 30-60%
More Room for Prompts - Send more data at once
Improved Parsing Accuracy - Explicit structure helps LLMs understand better
Reversible - Complete round-trip conversion from TOON back to JSON

How to Use

Enter your JSON data in the left input area. It will be converted in real-time, with TOON format results displayed on the right.

If there are syntax errors in the JSON, an error message will be displayed so you can correct and reconvert.

Conversion Options

Customize the output format according to your needs.

Delimiter

Select the character used to separate array elements and table rows.

Comma (,): Default. Common and readable
Tab (\t): Single character with highest token efficiency. Tabs rarely appear in natural language text
Pipe (|): Middle ground between comma and tab. Visually clear

Indent Width

Set the number of spaces used for indenting nested structures. Default is 2 spaces.

Key Folding

A feature that collapses deeply nested single-key chains into dot notation. This further reduces token count.

Off (Default) - Outputs in standard indented format. The structure is visually clear but uses more tokens.

Safe - Converts only safely foldable parts to dot notation. Key chains that meet the following conditions are eligible:

Only a single key exists at each level
Not an array
Value is not a complex object

For example, user.profile.name: "Alice" represents nesting in a single line, reducing indentation lines.

Example:

Original JSON:

{
  "user": {
    "profile": {
      "name": "Alice",
      "email": "alice@example.com"
    }
  }
}

TOON (Off):

user:
  profile:
    name: Alice
    email: alice@example.com

TOON (Safe):

user.profile.name: Alice
user.profile.email: alice@example.com

Key folding is particularly effective with API responses or configuration data with deep hierarchies. However, if there are multiple keys at the same level, or if you want to prioritize structural readability, keeping it Off is appropriate.

Token Efficient - Expresses the same data with 30-60% fewer tokens than standard JSON
Explicit Structure - Explicitly declares array length [N] and field names {fields}
Lossless Conversion - Full bidirectional conversion with JSON, no data loss
LLM Friendly - Explicit structural information improves LLM understanding and generation accuracy

Conversion Example

JSON:

{
  "users": [
    { "id": 1, "name": "Alice", "role": "admin" },
    { "id": 2, "name": "Bob", "role": "user" }
  ]
}

TOON:

users[2]{id,name,role}:
  1,Alice,admin
  2,Bob,user

When to Use TOON

TOON is particularly effective in the following cases:

Effective Scenarios:

Working with Uniform Array Data - Employee lists, product catalogs, log data—arrays of objects with the same fields benefit greatly from TOON's tabular format for significant token reduction
Bulk Data Input to LLMs - Reduce costs when sending large datasets for data analysis or report generation
Repeated API Calls - When sending the same format of data multiple times, token reduction effects accumulate
Saving Prompt Space - When you want to include multiple sample data or use together with system prompts

When JSON is Better:

Deeply nested non-uniform structures - Data with complex hierarchies and inconsistent fields
Small amounts of data - Token reduction benefits are minimal and not worth the conversion effort
Data to be generated by LLMs - Most LLMs are accustomed to generating JSON, so JSON is smoother as an output format

Learn More About TOON

TOON is a new format that emerged in 2025, with specifications being developed by the community.

For detailed specifications, benchmark results, and implementations in other programming languages, visit the official site:

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