TOML to YAML converter

Convert TOML to YAML (Cargo.toml, pyproject.toml, config files), with dates kept as ISO strings.

Converter

Indentation

TOML

Open file

YAML

Waiting for input

What you get

Convert TOML to YAML online: Cargo.toml, pyproject.toml or any TOML 1.0 config, with [[arrays of tables]] as YAML lists.
Strings YAML could misread, such as "2021" or "1.0", are quoted so they stay strings.
Checked twice: TOML read strictly, then the YAML parsed back and compared value by value.
Private and free: everything runs in your browser, nothing is uploaded, and there is no sign-up.

How each result is checked

Step 1: Your TOML is parsed with a TOML 1.0 parser; errors show the line number.
Step 1: The JSON is parsed back and compared with the parsed TOML, value by value.
Step 2: Your input is parsed with a strict, standards-compliant parser.
Step 2: The YAML output is parsed back with an independent YAML parser.
Step 2: The parsed-back data is compared with your original, value by value. Any difference is reported with its exact path.

What can't convert exactly

JSON has no date type, so TOML dates become ISO strings.
Comments are not carried over.
Integers larger than 9,007,199,254,740,991 can lose precision when any JavaScript tool reads JSON. You get a warning when your input has one.
Output follows YAML 1.2. Strings that YAML 1.1 readers (PyYAML, Ruby and other older libraries) would read as booleans, numbers or dates, such as yes, no, on, off, 1_000 or 2024-01-01, are quoted, so every YAML reader keeps them as strings.
Numbers are written by value: 1.0 becomes 1 and 1e3 becomes 1000. The result names any number whose written form changes, because some readers (Python, for example) treat 1 and 1.0 differently.

Questions

How is a two-step conversion checked?

Your input is converted to JSON first, then to the target format. Each step has its own independent check, and both must pass. The checks of both steps are listed under every result.

Is my data uploaded?

No. Everything runs in your browser, in a background worker. Nothing is sent to a server.

How do I convert TOML to YAML online?

Paste your TOML or open a file on the left (or click Example). The YAML appears on the right as you type, already checked. Copy it, or download it as a file. Nothing is uploaded.

Can the YAML output be wrong?

Every result is checked before it is shown (the checks are listed on this page). If a check fails, the page says "Review needed" and why, instead of presenting the output as correct, and anything that cannot convert exactly is named in the notes.