Question 1

What is json2toon.co?

Accepted Answer

json2toon.co is a free, browser-based JSON to TOON converter. It also converts between JSON, TOON, TONL, CSV, YAML, XML, TOML and Protobuf, and includes JSON repair, JSONPath queries, JSON Schema validation, a diff viewer and a JWT decoder. It is an independent tool built on the open-source TOON reference library; it is not the official TOON project.

Question 2

Is json2toon.co free to use?

Accepted Answer

Yes. The web converter, the browser extension and the public API are all free, with no account or signup..

Question 3

What is the TOON format?

Accepted Answer

TOON (Token-Oriented Object Notation) is a text format that encodes the same data model as JSON with less repeated syntax. Objects use YAML-style indentation, and arrays of objects with the same fields become a table: the field names are declared once in a header such as users[2]{id,name,role}: and each record is one comma-separated row. That removes the quotes, braces and repeated keys that make JSON expensive in LLM prompts.

Question 4

How is TOON different from TONL?

Accepted Answer

TOON is a compact serialization format focused on one job: fewer tokens in prompts. TONL (Token-Optimized Notation Language) is a separate format that adds a query API, schema validation, streaming and aggregation on top of a compact syntax. Use TOON for sending data to a model; consider TONL when you also need to validate or query the data in your own code.

Question 5

How many tokens does TOON save?

Accepted Answer

About 43% on average. In the official TOON v4.1 benchmark (5,856 LLM calls across four models), TOON used 42.6% fewer tokens than JSON. Savings depend on the shape of your data: flat uniform tables of records save the most (about 59%), while mixed or deeply nested structures save much less (about 33%). The converter shows the exact token counts for your own input, so you can check before you switch.

Question 6

When does TOON not help?

Accepted Answer

TOON gains little on deeply nested, irregular data where objects don't share fields, on single small objects, and on data that is mostly long free text. In those cases the structural overhead JSON adds is a small part of the total. If your pipeline needs strict JSON output from the model, keep JSON for the output and use TOON only for the input context.

Question 7

Does TOON hurt LLM accuracy?

Accepted Answer

Not in the published benchmark: TOON reached 72.2% retrieval accuracy versus 71.4% for JSON (a statistical tie) while using 42.6% fewer tokens. Results vary by model and task, so test with your own prompts. A short note in the system prompt explaining the table header syntax helps smaller models.

Question 8

Is my data uploaded anywhere?

Accepted Answer

No. Conversions in the web app run in a Web Worker inside your browser, so the data you paste never leaves your device. Only the public API processes data on a server, and only when you call it explicitly.

Question 9

Do you store my conversion history?

Accepted Answer

History is stored only in your browser's localStorage, and we have no access to it. Turn on Private Mode to disable history and analytics entirely. The setting syncs across open tabs.

Question 10

What formats are supported?

Accepted Answer

JSON, TOON, TONL, CSV, YAML, XML, TOML and Protobuf, in any direction. Every conversion goes through JSON as the intermediate model, so any pair works. Some formats can't represent everything: CSV has no nesting, and TOML needs a top-level table.

Question 11

Can I convert multiple files at once?

Accepted Answer

Yes. Batch mode in the converter accepts several files, converts them all to the target format, and lets you download the results as a single ZIP archive.

Question 12

Can I share a conversion?

Accepted Answer

Yes. The share button encodes your input and settings into the URL, so anyone with the link sees the same conversion. The data lives in the link itself and is not stored on our servers.

Question 13

Is there a browser extension?

Accepted Answer

Yes. The free Chrome extension converts JSON to TOON from a popup or the right-click menu, using the same conversion logic as the website.

Question 14

Is there an API?

Accepted Answer

Yes. POST your content to https://json2toon.co/api/v1/toon to get TOON back. It accepts JSON, YAML, TOML or XML input and auto-detects the format if you don't specify one. It is free and needs no key. Examples and limits are at /toon-api and the full reference is at /api-docs.

Question 15

Can I use TOON in my CI/CD pipeline or code?

Accepted Answer

Yes. For TypeScript and JavaScript, install the official @toon-format/toon package and call encode() and decode() directly; libraries exist for other languages too (see the installation guides). For one-off scripts, the public API works from any HTTP client.

Question 16

What browsers are supported?

Accepted Answer

Current versions of Chrome, Firefox, Safari and Edge. The converter needs JavaScript and Web Worker support.

Frequently Asked Questions

General

Token savings

Privacy & Security

Features

Developers