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TOML Validator

Validate TOML configuration files against the TOML 1.0 spec and convert to JSON.

Conforms to the TOML 1.0.0 specification (RFC-compliant parser).

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Validate TOML configuration files against the TOML 1.0.0 specification and convert them to JSON. Get precise error messages with line and column numbers for Cargo.toml, pyproject.toml, and any other TOML config.

[x]Features
  • -Full TOML 1.0.0 spec support (smol-toml parser)
  • -Errors reported with exact line and column
  • -One-click TOML to JSON conversion
  • -Key/value pair and nesting depth stats
  • -Automatic re-validation as you type
>Use Cases
  • >Linting Cargo.toml before a build
  • >Checking pyproject.toml syntax
  • >Converting legacy TOML configs to JSON
  • >Learning TOML syntax with instant feedback

Frequently Asked Questions

>Which TOML version does it support??
The full TOML 1.0.0 specification, including multiline strings, arrays of tables, inline tables, and date-time values.
>Is my TOML sent anywhere??
No — parsing happens in your browser with the smol-toml library. Nothing is uploaded.
>Can I use it for Cargo.toml or pyproject.toml??
Yes. Cargo.toml and pyproject.toml are valid TOML and will parse (note: tools like Cargo may ignore unknown keys with a warning — this validator reports spec compliance, not tool semantics).