TOML Formatter & Validator Free Online
Validate, format, and convert TOML to JSON. Paste any TOML config file to check syntax, pretty-print it, and get the JSON equivalent instantly. Runs in your browser.
TOML Input
JSON Output
JSON Input
TOML Output
Pro — TOML v1.1, batch file conversion, TOML linter, API access
API access · Priority queue · Team workspace
How It Works
Paste Your TOML
Paste any TOML configuration file into the input panel. You can also click Sample to load an example covering common TOML features: sections, arrays, inline tables, and multi-line strings.
Validate & Parse
The parser validates your TOML and shows a green "Valid TOML" badge or a red error message pointing to the first problem found. Valid configs are parsed into their data structure immediately.
Copy JSON Output
The parsed data is shown as pretty-printed JSON in the right panel, ready to copy. Switch to the JSON → TOML tab to do the reverse conversion for generating config files from data.
TOML Formatter Features
Validation, pretty-print, and bi-directional TOML ↔ JSON conversion
Syntax Validation
Every keystroke validates the TOML and shows a clear green or red indicator. Error messages include line context to help you pinpoint the problem quickly.
Bi-Directional Conversion
Convert TOML to JSON for APIs and code, or convert JSON back to TOML for generating config files. Both directions produce clean, formatted output.
Full TOML Support
Handles all TOML v1.0 features: strings, integers, floats, booleans, dates, arrays, inline tables, array of tables, and multi-line strings.
Real-Time Parsing
Results update as you type — no need to click a submit button. Useful for quickly editing a config and instantly seeing how the parsed structure changes.
One-Click Copy
Click Copy to put the full JSON or TOML output onto your clipboard, ready to paste into code, config files, or documentation.
100% Offline
All parsing runs in your browser. No TOML config data is ever sent to a server, keeping sensitive settings like database credentials or API keys private.
Free vs Pro
| Feature | Free | Pro |
|---|---|---|
| TOML syntax validation | ||
| TOML → JSON conversion | ||
| JSON → TOML conversion | ||
| TOML v1.1 features | — | |
| Batch file conversion | — | |
| REST API access | — |
Frequently Asked Questions
TOML (Tom's Obvious Minimal Language) is a configuration file format designed to be easy to read. It is used by Cargo (Rust), Poetry (Python), Hugo, and many other tools. Its syntax is more explicit than YAML and avoids indentation ambiguity.
The tool supports the full TOML v1.0 spec: strings (basic, literal, multiline), integers, floats, booleans, offset date-times, local dates/times, arrays, inline tables, tables ([section]), and arrays of tables ([[array]]).
Many APIs and JavaScript libraries consume JSON. Converting a TOML config to JSON lets you inspect the parsed structure, use jq to query it, or feed it to tools that don't natively understand TOML.
Yes. Switch to the JSON → TOML tab, paste valid JSON, and a TOML equivalent is generated. Note that some JSON structures (e.g. null values, mixed-type arrays) are not representable in TOML — the converter will flag these.
TOML is more explicit — it has strict type rules, no indentation dependency, and unambiguous section headers. YAML is more compact but notoriously tricky (e.g. Norway problem). TOML is preferred for config files where clarity matters.
No. All parsing and conversion runs in your browser using JavaScript. No TOML or JSON data is ever transmitted to any server, keeping sensitive credentials and settings private.