JSON to TOML

JSON is the interchange format of APIs and programs, but as a config file for humans TOML is more pleasant: sections in square brackets, plain key-equals-value lines and comments keep it tidy. This tool serialises your JSON object into well-formed TOML, like the kind Cargo.toml or pyproject.toml use.

The conversion runs entirely locally in your browser (smol-toml, pure JavaScript). Objects become tables, nested objects become sub-tables (such as [server.meta]), arrays become TOML arrays and strings, numbers and booleans become scalars. Because a TOML document needs a table at the top level, an array, scalar or null at the root is rejected with a clear message instead of failing cryptically.

You will meet this when generating a Cargo or pyproject configuration from a template, turning settings a program emitted as JSON into a hand-editable .toml, or producing a readable config from an API. Honestly: TOML has no null type - objects with null values are rejected with a clear message, not silently dropped. Nothing is uploaded.

An honest note on the limits: TOML has no null value and no mixed types within the same array. If your JSON contains such constructs, they cannot be mapped losslessly - the tool makes that transparent rather than silently producing something invalid or wrong.

Specifications

In 3 steps

1. Drop or pick your JSON file.
2. The tool serialises it to TOML.
3. Download the TOML file.

Limitations: Expects a JSON object at the top level; an array, scalar or null at the root is rejected with a clear message. Nested objects become sub-tables, arrays become TOML arrays. TOML has no null type, so objects with null values are rejected. Key order follows the JSON.

FAQ

Related tools

TOML to JSON · JSON to YAML · YAML to JSON · YAML to TOML · OBJ to GLB · GLB to OBJ