TOML Validator
This TOML validator checks that a document parses and reports the first error with its line and column when it does not, which is what turns a vague failure into a fix. Valid documents get a breakdown of the tables and keys the file defines, so you can confirm the structure is what you intended — a table nested one level too deep parses perfectly and behaves nothing like you expected. Most TOML errors come down to the same handful of mistakes: a duplicate key, a table defined twice, a bare string that needed quoting, or an array left unclosed across several lines.
How it works
Checks that a TOML document parses and reports the first error with its line and column when it does not. Valid documents get a breakdown of the tables and keys the file defines.
Most TOML errors are the same handful of mistakes: a duplicate key, a table defined twice, an unquoted string that needed quoting, or a missing closing bracket on an array.
Everything runs in your browser — nothing you paste is sent to a server.
The errors you will actually hit
- Duplicate key — TOML forbids defining the same key twice, unlike some other formats which silently take the last one.
- Table defined twice — the same
[header]appearing more than once. - Unquoted string — a bare value containing a space, a colon or a hash needs quotes.
- Unclosed array — arrays may span lines, so a missing bracket is reported far below where it started.
- Key after a table header — a bare key written after
[section]belongs to that section, which is often not what was meant.
Valid is not the same as correct
This is the failure mode that costs the most time. A key placed inside the wrong table parses without complaint and is then silently ignored by the tool reading it, because the tool is looking somewhere else.
That is why the table list is shown for valid documents: it is the quickest way to confirm the structure matches what you had in mind.
Frequently asked questions
How do I validate TOML?
Paste your document into the panel. It is checked as you type, with any error reported by line and column.
What are the most common errors?
A duplicate key, the same table defined twice, an unquoted string that needed quotes, and an array left unclosed across several lines.
Why does it list the tables?
Because a structural mistake often parses perfectly. Seeing the tables the file actually defines is how you catch a section nested one level deeper than you intended.
Does valid TOML mean my config is correct?
No. It means the syntax is right. Whether the keys are the ones your tool expects is a separate question the format cannot answer.
Which TOML version does it check?
TOML 1.0, the current stable specification.
Is my config uploaded?
No. Validation runs entirely in your browser.
Related tools
TOML to JSON Converter
This TOML to JSON converter keeps every type the format distinguishes.
JSON to TOML Converter
This JSON to TOML converter writes nested objects as tables and arrays as [[tables]].
YAML Validator
This YAML validator parses your document and reports the first error with its line and column.