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TOML / JSON Converter

Convert and format between TOML and JSON. View syntax errors, copy and download.

Last updated: 2026/10/16 Developer Feedback & bug reports
Input

How to Use

1

Enter Data

Paste your TOML or JSON into the input box — config files (Cargo.toml, pyproject.toml) or API responses work as-is.

2

Choose Direction

Click "TOML → JSON" or "JSON → TOML" and the formatted result appears in the output box.

3

Use the Result

Copy to clipboard, or download the result as a .json / .toml file.

About the TOML / JSON Converter

A web tool that converts between TOML (Tom's Obvious, Minimal Language) and JSON (JavaScript Object Notation). It bridges TOML — widely used in Rust's Cargo.toml, Python's pyproject.toml, and many app config files — with JSON, the dominant format for APIs and program interchange. It supports the main syntax including tables, arrays, inline tables, arrays of tables, and multiline strings. All processing happens entirely in your browser, so your input is never sent to any server — even sensitive config files stay private.

Features

  • Two-way ConversionTOML→JSON and JSON→TOML, both with a single click.
  • Main Syntax SupportCorrectly handles tables, arrays of tables, inline tables, multiline strings, numbers and datetimes.
  • Syntax ErrorsInvalid input shows an error with the line number so you can fix it fast.
  • Privacy ProtectedAll conversion runs in your browser. Data is never sent to servers.

Use Cases

  • Inspect and edit Rust Cargo.toml or Python pyproject.toml
  • Convert TOML config into JSON for programmatic use
  • Convert JSON config into readable TOML
  • Convert static-site config files (Hugo, Netlify, etc.)
  • Validate config syntax and standardize formatting

FAQ

Is the TOML / JSON converter free?
Yes, it is completely free. No registration or installation required.
Is my data sent to a server?
No. All conversion runs locally in your browser and is never sent or stored externally, so even sensitive config files are safe.
Are TOML comments preserved after conversion?
No. Comments (lines starting with #) are lost when converting TOML to JSON, because JSON has no comment syntax. Keep important notes outside of comments.
How are JSON null values handled?
TOML has no equivalent of null, so keys with null values are omitted from the output when converting JSON to TOML. Keep your data as JSON if you need to preserve nulls.
How are datetimes converted?
TOML dates, times, and datetimes are converted to RFC3339 strings in JSON. Note that they are treated as plain strings on the JSON side.
What causes a "syntax error"?
For TOML: a missing "=", unterminated strings or brackets, or invalid key names. For JSON: trailing commas, single quotes, or comments. Use the line number in the error message to locate the issue.

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