Validate TOML configuration file syntax with error reporting and formatted JSON output conversion.
Paste TOML into the box and run the check: the tool returns a verdict - valid, or the first syntax error with its line and column - and for valid input it shows the document converted to formatted JSON. The check runs entirely in the page, so the text never leaves your browser. The most common surprise is JSON habits carrying over: trailing commas in arrays are an error, and a bare key with a dot such as a.b = 1 builds a nested table instead of one key.
A concrete input and expected output from the current implementation.
Input
title = "TOML Example" [database] enabled = true ports = [8000, 8001]
Expected output
{
"title": "TOML Example",
"database": {
"enabled": true,
"ports": [8000, 8001]
}
} Tables in TOML map to nested JSON objects, so [database] becomes the "database" object, while booleans, integers, and strings keep their types. The JSON is shown formatted for inspection.
The text is checked against the TOML grammar token by token. The first invalid construct stops the run and is reported with its line and column, so a file with several errors needs repeated fixes. Duplicate keys, trailing commas, unterminated strings, malformed dates, and unknown escape sequences are all rejected.
On a successful parse, TOML values are mapped to JSON: tables become objects, arrays of tables become arrays of objects, inline tables become objects, and strings, booleans, integers, and floats keep their kinds. Dates and times become strings, because JSON has no date type. Quoted keys - including keys that contain dots - become ordinary JSON property names.
Syntax validity and what your program requires are different things. The file may lack keys or entries your program needs, a value may be a string where your program expects an integer, or your program's parser may implement a different version or dialect of TOML. Take a minimal reproduction file and compare the two parsers' complaints.
Yes. Under the TOML rules, defining the same key twice in the same table, and redefining a table that already exists, are errors and are reported. Duplicates in different tables are fine, because each table is its own namespace, and two keys that differ only in case are two different keys.
The example and behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.
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