What happens to a JSON key that isn't a valid bare TOML key, like one containing a space?

It gets wrapped in double quotes automatically: {"first name": "Alice"} becomes "first name" = "Alice". A key using only letters, digits, underscores, and dashes needs no quoting and is left bare, even one starting with a digit, TOML's bare-key rule allows that.

I need a value to come out as a TOML float, like price = 5.0, not an integer. Why does it come out as 5 instead?

JSON and JavaScript don't distinguish 5.0 from 5, they're the exact same number. That distinction is already gone by the time your JSON reaches this converter, so there's no way to recover whether you originally meant a float or an integer. If a downstream TOML consumer requires the float form specifically, edit the output by hand after converting.

JSON to TOML Converter: Export JSON as TOML Config Online

JSON Inputpaste or type · or drop a .json file

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TOML Output

Convertedjson-to-toml

JSON to TOML: from API response to config file

When you're scaffolding a new Rust crate, Python package, or CLI tool, you often start from a JSON example (an API response, a design doc) and need it as a real Cargo.toml or pyproject.toml.

This converter turns any JSON object into equivalent TOML: nested objects become tables, arrays of objects become arrays of tables ([[items]]).

What TOML cannot represent

TOML's type system is deliberately small, and two common JSON shapes have no TOML equivalent.

Top-level arrayNot allowed — TOML documents must be a table (object) at the root

nullNo null literal exists in TOML — remove the key or give it a real value

Nested objects & arraysFully supported, as tables and arrays of tables

Why the converter refuses instead of guessing

Some TOML libraries silently drop null fields rather than erroring, which quietly changes your data. This tool checks for both cases first and tells you exactly which key is the problem, so nothing gets lost without you knowing.

Everything runs locally: it is safe to paste config values that include internal package names or private registry URLs.

Frequently asked questions

No. This direction has no way to tell an ISO-8601-looking string apart from any other string, so it's written out as a quoted TOML string, "2024-01-15T09:00:00Z", not the unquoted native date-time type TOML also supports. Both read back as the same value in most tools, but it isn't a byte-for-byte round trip of an original TOML file.

JSON → TOML

JSON to TOML: from API response to config file

What TOML cannot represent

Why the converter refuses instead of guessing

Frequently asked questions