Online TOML Validator [2025]

TOML stands for Tom's Obvious, Minimal Language. It's a configuration file format designed to be easy to read due to its straightforward semantics. TOML aims to map unambiguously to a hash table (or dictionary) and is often used for application configuration files because of its clarity compared to formats like JSON or YAML for this specific purpose.

Key features include key/value pairs, sections (tables), arrays, and support for various data types like strings, integers, floats, booleans, dates, and times.

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  Prevent Runtime Errors:

  Incorrect syntax in configuration files can cause applications to fail at startup or behave unexpectedly. Validation catches these errors early.

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  Ensure Consistency:

  Validating ensures your TOML files adhere to the official specification, promoting consistency across projects and teams.

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  Debugging Aid:

  When configuration isn't working as expected, validating the file is a crucial first step in debugging to rule out syntax issues.

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  Save Time:

  Quickly pinpoint syntax mistakes instead of manually scanning large configuration files.

• Missing quotes around strings: `key = value` instead of `key = "value"`
• Incorrect date/time format: `dob = 27-05-1979` instead of `dob = 1979-05-27`
• Using single quotes for multi-line strings without triple quotes: `'line1\nline2'`
• Defining the same table twice: `[database]` ... `[database]`
• Mixing data types in arrays intended to be uniform (though TOML allows mixed-type arrays, some parsers might be stricter or applications might expect uniformity).
• Invalid escape sequences within strings.
• Missing commas between elements in an array: `ports = [ 8001 8002 ]`

Our validator will help you identify these and other syntax issues based on the TOML v1.0.0 specification.