Does formatting keep comments?

No. Formatting re-serializes after parsing, so comments and blank-line styling are lost — back up with version control first.

What is the difference between [table] and [[table]]?

[table] defines a sub-table (an object); [[table]] appends a table to an array of the same name (an array of objects). Switch to TOML -> JSON mode to see the difference clearly.

What are the limits of JSON to TOML conversion?

TOML does not support null values — fields containing null raise an error, and the top level must be an object.

TOML Validator & Formatter

Free online TOML validator and formatter: line-and-column error hints, normalized layout and JSON conversion — local.

Privacy: all processing happens locally in your browser. Your input never leaves your device.

What is TOML Validator & Formatter?

Rust's Cargo.toml, Python's pyproject.toml and many static site generators use TOML. Its stricter syntax avoids YAML's indentation traps, but arrays of tables and nested tables still take getting used to. This tool validates TOML in real time with clear line-and-column errors, normalizes the layout, and converts to JSON so you can confirm the structure your config actually parses into.

How to Use

Paste TOML content
Syntax errors are flagged instantly with line and column; click to format the layout
Switch to TOML -> JSON mode to confirm the parsed structure

FAQ

Does formatting keep comments?: No. Formatting re-serializes after parsing, so comments and blank-line styling are lost — back up with version control first.
What is the difference between [table] and [[table]]?: [table] defines a sub-table (an object); [[table]] appends a table to an array of the same name (an array of objects). Switch to TOML -> JSON mode to see the difference clearly.
What are the limits of JSON to TOML conversion?: TOML does not support null values — fields containing null raise an error, and the top level must be an object.

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Last updated 2026-09-04