What is TONL and why would I use it over JSON?

TONL (Token-Optimized Notation Language) represents the same structured data as JSON but avoids repeating field names and punctuation across rows. For tabular data sent to an LLM, that means fewer tokens per request without losing the information.

How much smaller is TONL than JSON?

It depends on your data — highly repetitive tabular data with many rows saves the most, since the field names are written once instead of per record. The tool shows an estimated token count for your specific input so you can measure the actual saving.

Does the token estimate match my model's tokenizer exactly?

It's an estimate. Different models tokenize slightly differently, so treat the number as a relative comparison between input and output rather than an exact billing figure.

My CSV columns came out wrong — what happened?

Check the delimiter setting and whether the first row is marked as a header. A CSV using semicolons or tabs needs that delimiter selected, otherwise the whole row is read as one column.

Is my data uploaded anywhere?

No. The conversion runs entirely in your browser, so your CSV or JSON never leaves your device.

CSV/JSON → TONL Converter

Convert CSV or JSON into TONL (Token-Optimized Notation Language) for compact, LLM-friendly structured data.

Options

Input Settings

Format

CSV delimiter

CSV options

TONL Settings

Encoding

TONL delimiter

Indent

Input

TONL Output

About CSV/JSON → TONL Converter

When you feed structured data to a large language model, every repeated key and bracket costs tokens — and tokens cost money and eat into the context window. A JSON array of a hundred records repeats each field name a hundred times. TONL (Token-Optimized Notation Language) keeps the data readable while stripping that redundancy, which is why it can meaningfully shrink the payload you send to a model.

This converter takes the CSV or JSON you already have and turns it into TONL. Paste a CSV export from a spreadsheet or a JSON response from an API, pick your encoding options, and get compact TONL out the other side — along with an estimate of how many tokens you saved versus the original. That estimate lets you decide whether the trade is worth it for your prompt.

Conversion runs in your browser, so datasets stay on your machine. Tune the delimiter, indentation, and whether to include type hints to match what your downstream prompt or parser expects.

How to use CSV/JSON → TONL Converter

Choose your input format
Select CSV or JSON. For CSV, set the delimiter and whether the first row is a header so columns map to field names correctly.
Paste your data
Drop a CSV export or a JSON array into the input pane. The built-in example shows the expected shape if you need a starting point.
Set the TONL options
Pick a delimiter and indent level, and toggle smart encoding or type hints depending on how compact versus explicit you want the output.
Convert and check the savings
Run the conversion, then read the token estimate to see how much smaller the TONL is than the original before copying it into your prompt.

Frequently asked questions

JSON ⇄ TOON Converter

Convert between JSON and TOON (Token-Oriented Object Notation) format. TOON reduces LLM token usage by 30-60% for structured data while maintaining readability.

JSON Formatter · Beautifier · Validator

Format, minify, sort keys, and validate JSON/JSONC/JSON5 with optional JSON Schema validation. Supports comments and trailing commas.

YAML ⇄ JSON Converter

Instantly convert data between YAML and JSON formats with real-time updates and syntax highlighting.

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