JSON to TOON Converter - Reduce LLM Token Usage

Input

Output

What is JSON to TOON Converter?

Need to convert your JSON (JavaScript Object Notation) data to TOON (Token-Oriented Object Notation)? This tool does that instantly. TOON is a compact text format built for feeding structured data to LLMs: an array of objects with the same keys is written once as a header plus one comma-separated row per item, instead of repeating every key.

That's where the savings come from, so they depend on your data. A list of 200 orders with the same fields shrinks a lot; deeply nested or irregular objects save little and can even come out longer than minified JSON. The TOON spec and README has benchmarks if you want numbers for your model. Paste your own data, compare, and decide. Learn more about JSON at MDN.

Everything happens in your browser – your data stays private. Convert, download, and use your TOON right away. You can also format your JSON first using our JSON Formatter or validate it with our JSON Validator.

What Makes This Tool Different

Token Savings

Uniform arrays of objects lose their repeated keys, braces and most quotes, which is usually where JSON spends its tokens. Check the result against your own data and tokenizer.

Lossless Conversion

Objects, arrays, strings, numbers, booleans and null all map to TOON, and decoding the output gives back the same values. Integers longer than JavaScript can hold exactly, like a 19-digit ICCID, are written with every digit.

Instant Processing

Conversion happens in milliseconds. Paste your JSON, and get optimized TOON instantly. No waiting, no server delays – pure browser-side processing.

Smart Formatting

TOON uses intelligent formatting – tabular data becomes compact rows, nested structures use indentation, and arrays are optimized for readability.

File Upload Support

Got a JSON file? Just upload it. Works with .json and .txt files. No need to copy-paste – just drag and drop or click upload.

Download TOON

One click to download your converted TOON as a .toon file. Perfect for saving, sharing, or using with LLM applications.

How It Works

Paste or Upload JSON

Paste your JSON data into the left editor, or click "Upload" to load a file. You can also click "Sample" to see example JSON. The tool accepts any valid JSON structure – objects, arrays, nested data.

Automatic Conversion

As soon as you paste, the converter processes your JSON and displays the optimized TOON format on the right. The conversion is instant and preserves all your data structure, types, and values perfectly.

Copy or Download

Use "Copy" to paste the TOON somewhere else, or "Download" for a .toon file on disk. The TOON format is optimized for LLM token efficiency while remaining human-readable.

When You'd Actually Use This

LLM Applications

Working with Large Language Models? Convert a JSON list of records to TOON before pasting it into a prompt, and the repeated keys are written once instead of on every row, which usually cuts the token count.

API Responses

Sending data to LLMs via APIs? TOON format reduces payload size and token costs. Perfect for optimizing API responses before sending to ChatGPT, Claude, or other LLMs.

Database Records

Exporting database records for LLM processing? TOON's tabular format is perfect for uniform record sets. Convert JSON exports to TOON for efficient LLM consumption.

Time-Series Data

Working with analytics, metrics, or logs? TOON's compact format is ideal for time-series data with consistent fields. Reduce token costs when processing large datasets with LLMs.

Common Questions

Is my JSON data stored?

No. All conversion happens in your browser using the @toon-format/toon library. Your data never leaves your computer. The library is available on npm for Node.js applications.

What JSON formats are supported?

We support all valid JSON according to the ECMA-404 standard. Objects, arrays, nested structures, strings, numbers, booleans, null – everything standard JSON supports.

Can I convert invalid JSON?

No. The converter validates your JSON first. If it's invalid, you'll see an error message. Fix the syntax error, then convert again. Use our JSON Validator to check your JSON first.

Is the conversion lossless?

For values, yes: every string, number, boolean, null, object and array comes back the same when you decode the TOON. Long integers keep all their digits. What changes is spelling, not data: 1.0 is written as 1, and the indentation is TOON's own.

How much token savings can I expect?

It depends on the shape. Tabular data (lists of objects with the same keys) sees the biggest drop, because keys appear once in the header. Deeply nested or non-uniform data saves much less and can be larger than compact JSON. The TOON spec and README publishes benchmarks; for your case, run both versions through your model's tokenizer.

Can LLMs understand TOON format?

Yes! TOON is designed to be LLM-friendly. Modern LLMs like GPT-4, Claude, and others can parse and understand TOON format just as well as JSON, but with significantly fewer tokens.

Other TOON Tools You Might Need

Converting JSON to TOON is just one TOON task. Here are other tools that work well together: