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Free JSON to TOON Converter

Convert JSON to TOON format and cut LLM prompt tokens by up to 60%.

About this tool

TOON (Typed Object Oriented Notation) is a lightweight, human-readable data format specifically designed to minimize token usage when communicating with Large Language Models (LLMs) like ChatGPT, Claude, and Gemini. When you send large JSON payloads in a prompt, the brackets, quotes, commas, and heavy formatting consume a massive amount of your context window (and budget). TOON strips all of this away while preserving the exact data structure. Converting JSON to TOON before injecting it into your prompt can cut token usage by up to 60%. This bidirectional converter lets you instantly translate JSON into TOON for your prompts, or decode TOON back into JSON when testing API responses. It runs entirely in your browser using the official @toon-format/toon library.

How to use

Step 1: Select your conversion direction using the JSON → TOON or TOON → JSON toggle.
Step 2: Paste your data into the left input box.
Step 3: Click Convert to transform the payload.
Step 4: When converting to TOON, notice the Token Savings estimate to see how much prompt context you saved.
Step 5: Click Copy to use the optimized payload in your LLM prompt.

Frequently Asked Questions

TOON is an ultra-minimal data serialization format optimized for LLMs. It removes quotes around keys, removes commas, and uses a simplified indentation/type system. LLMs understand it perfectly natively because they are trained on vast amounts of structured text.

Minified JSON removes spaces but keeps all the quotes and brackets, which tokenizers split into separate tokens. TOON removes the syntax characters entirely, resulting in far fewer actual tokens, which saves you money and context space.

Yes! Modern LLMs (GPT-4, Claude 3, Gemini) excel at reading structured text. Because TOON uses clear key-value pairs and indentation, LLMs parse it just as accurately as JSON, but much faster.

No. TOON strictly preserves arrays, objects, strings, numbers, and booleans. Converting JSON to TOON and back to JSON will result in the exact same data structure.

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