TOON (Token-Oriented Object Notation) is a data serialization format designed specifically for LLM prompts to be highly efficient. It dramatically reduces token usage by 30-60% compared to JSON while remaining structured and human-readable. By using a tabular format for arrays and minimal syntax for objects, TOON makes your data cheaper and faster to process with AI models.

What's the difference between TOON and JSON?

The key difference is token efficiency. JSON is verbose, with brackets, quotes, and commas that consume tokens. TOON is a more compact syntax designed for LLMs, representing arrays as tables with headers and using minimal punctuation. This efficiency directly translates to significant cost savings on your LLM API bills, especially for large or repeated datasets.

How much can I save with TOON?

You can typically expect to save 30-60% on LLM tokens compared to using JSON. For large datasets or frequent API calls, this translates directly into significant cost savings. Data with repeated structures, like API responses or database results, often sees savings at the higher end of this range (40-60%).

Is TOON compatible with all LLMs?

Yes. TOON is a simple text format that works flawlessly with all major large language models, including those from OpenAI (GPT-4), Anthropic (Claude), Google (Gemini), and Meta (LLaMA). Since any LLM can process plain text, they can all be instructed to understand and parse the TOON format with a simple instruction in your prompt.

Can I convert TOON back to JSON?

Absolutely. TOON is fully and losslessly reversible. Our converter tool supports bidirectional conversion, meaning you can convert TOON back to the exact original JSON structure without any data loss. This allows you to use TOON for efficiency and then convert back to JSON for compatibility with other tools.

What types of data work best with TOON?

TOON can represent any valid JSON data, but it delivers the highest token savings (40-60%) on uniform tabular data. This includes database query results, API responses with lists of objects, analytics data, or product catalogs. While TOON fully supports nested objects and arrays, the token reduction is most dramatic with flatter, more repetitive data structures.

Is my data safe when using this converter?

100% safe. All conversion from JSON to TOON (and back) happens locally in your browser. Your data is never sent to any server, never stored, and never seen by us. The converter even works offline once the page has loaded, guaranteeing your information remains private.

Yes, completely free. Both this TOON converter and the underlying TOON format specification are open and free to use without any limits, file size restrictions, or premium features. It's an open-source effort to make working with LLMs more efficient for everyone.

利用規約

最終更新日: 12/27/2025

1. 規約への同意

JSON to TOON Converter (「サービス」) にアクセスして使用することにより、お客様は本契約の条項および条項に拘束されることに同意し、同意することになります。

2. サービスの説明

このサービスは、JSON 形式と TOON 形式の間でデータを変換するためのクライアント側ツールを提供します。本サービスは「現状のまま」提供され、個人的かつ非営利的な使用を目的としています。

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4. 責任の制限

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5. 規約の変更

当社は、独自の裁量によりこれらの規約を随時変更する権利を留保します。したがって、このページを定期的に確認する必要があります。かかる変更後もサービスを継続して使用することにより、新しい規約に同意したものとみなされます。