TOML Validator
Paste TOML and get instant validation. If valid, you see the parsed structure as JSON; if invalid, you get the line and message of the first error.
Last updated: May 27, 2026
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Buy me a coffeeWhat is TOML Validator?
TOML is a configuration file format favored by Cargo, Poetry, Hugo, and many other tools. Its strict-but-readable rules make it easy to write by hand, but small mistakes — a missing equals sign, an unquoted special character, an unintended duplicate key — are common. A validator catches them before you run your build.
This tool parses TOML 1.0 (the current stable spec): bare and quoted keys, dotted keys, tables, arrays of tables, inline tables, basic strings, literal strings, multi-line strings, integers (decimal/hex/octal/binary), floats, booleans, and date-time literals. When validation succeeds, the parsed structure is shown as JSON so you can see exactly how the parser interpreted your input.
How to Use TOML Validator
Paste TOML into the input panel.
Validation runs as you type.
If valid, the parsed JSON appears on the right.
If invalid, the line and message of the error appear instead.
Common Use Cases
- Verifying a Cargo.toml or pyproject.toml before committing.
- Catching duplicate-key or duplicate-table errors that Cargo would reject.
- Inspecting how a TOML parser will interpret a tricky multi-line string.
- Debugging unexpected nesting in a TOML config.
Example Input and Output
A simple TOML document parses to a JSON object.
title = "Example"
[server]
port = 8080{
"title": "Example",
"server": {
"port": 8080
}
}Privacy
All TOML parsing happens in your browser. No content is sent to a server.
Dates
TOML datetime literals are preserved as ISO-8601 strings in the JSON view since JSON has no native datetime type.
inf and nan
TOML 1.0 supports inf, +inf, -inf, and nan numeric literals. Since JSON does not, the JSON view renders them as strings "Infinity", "-Infinity", and "NaN".