TONL to JSON Converter

Input TONL

or drop a file anywhere

Output JSON

Your JSON appears here as you type.

Paste data to see token savings

Convert TONL to JSON with our free online converter.

Example: TONL input and real JSON output

The output below was generated by the same conversion code the converter uses, run on this sample when the page was built.

TONL input (228 characters)

#version 1.0
root:
  events[4]{latencyMs,level,service,ts}:
    42,info,auth,"2026-09-30T08:12:04Z"
    310,warn,billing,"2026-09-30T08:12:09Z"
    38,info,auth,"2026-09-30T08:12:15Z"
    1204,error,search,"2026-09-30T08:12:21Z"

JSON output (505 characters)

{
  "events": [
    {
      "latencyMs": 42,
      "level": "info",
      "service": "auth",
      "ts": "2026-09-30T08:12:04Z"
    },
    {
      "latencyMs": 310,
      "level": "warn",
      "service": "billing",
      "ts": "2026-09-30T08:12:09Z"
    },
    {
      "latencyMs": 38,
      "level": "info",
      "service": "auth",
      "ts": "2026-09-30T08:12:15Z"
    },
    {
      "latencyMs": 1204,
      "level": "error",
      "service": "search",
      "ts": "2026-09-30T08:12:21Z"
    }
  ]
}

JSON output is 121% larger than the TONL input. The same data is 329 characters as minified JSON and 505 as pretty-printed JSON. Sizes are character counts, not tokens: token counts depend on the model's tokenizer (see the tokenizer comparison).

TONL to JSON: what changes

Reading TONL: TONL documents start with a #version line and wrap the data in root. The TONL encoder writes object keys in alphabetical order, so the original key order is not kept.
Writing JSON: Output is pretty-printed with your chosen indentation. JSON is the safest target when the data goes into code, an API, or another tool.

About TONL

TONL (Token-Optimized Notation Language) is a compact text format that maps one-to-one to JSON and ships with a query API, schema validation, and streaming. Savings are roughly 32-45% versus JSON in the TONL project's own measurements.

✓Lossless round trip to JSON
✓Query and aggregation API
✓Schema validation (TSL)
✓Streaming for large files

Full TONL Documentation →

About JSON

JavaScript Object Notation is the most widely used data interchange format. Lightweight, easy to parse, and supported by every programming language.

✓Universal compatibility
✓Easy to parse
✓Great for APIs
✓Native in JavaScript

Full JSON Documentation →

Why Convert TONL to JSON?

Use JSON when you need maximum compatibility with other systems, APIs, or programming languages. It's the de facto standard for web APIs and data exchange.

TONL to JSON: Frequently Asked Questions

How do I convert TONL to JSON?

Paste your TONL into the editor on json2toon.co. The tool detects the input and produces JSON instantly, then you copy the result. Conversion runs entirely in your browser, so nothing is uploaded to a server.

Is the TONL to JSON converter free?

Yes. Converting TONL to JSON on json2toon.co is free with no account, signup, or usage limit. A free public API is also available for automated, programmatic conversion.

Why convert TONL to JSON?

Convert TONL to JSON with our free online converter.

What should I watch out for when converting TONL to JSON?

Output is pretty-printed with your chosen indentation. JSON is the safest target when the data goes into code, an API, or another tool.

Is my data safe when I convert TONL to JSON?

Yes. The TONL to JSON conversion happens client-side in your browser. Your source data stays on your device and is never sent to or stored on a server, which makes it safe for private or sensitive payloads.