📋 TOML Validator

What Can the TOML Validator Do?

The TOML Validator is a free online tool that helps developers validate the syntax of TOML files. It automatically detects format errors, duplicate keys, invalid values, and other issues, with formatting and JSON conversion features. All validation is done locally in your browser.

Core Features

• Syntax Validation: Check TOML syntax correctness, detect missing equals signs, duplicate keys, invalid values
• Format Beautify: One-click TOML formatting with consistent indentation and style
• JSON Conversion: Convert TOML to JSON for use in JavaScript and other environments
• Error Location: Precise line-number error messages for quick problem identification
• Drag & Drop: Drag and drop .toml files into the input area

How to Use

1. Paste TOML content in the input box, or drag & drop a .toml file

2. Click "Validate" to see validation results

3. Fix errors based on line number hints

4. Click "Format" to beautify TOML content

5. Click "To JSON" to see JSON output

6. Copy or download the result

Use Cases

Case 1: Config File Validation

Validate Rust Cargo.toml, Python pyproject.toml, and other config files for syntax correctness.

Case 2: Config Format Conversion

Convert TOML configs to JSON for applications or APIs that require JSON format.

Case 3: Team Collaboration

Validate config files before committing to ensure correct format and avoid CI/CD build failures.

Case 4: Learning TOML

Learn TOML syntax through real-time validation, understanding tables, array tables, and inline tables.

Technical Background

TOML (Tom's Obvious Minimal Language) is a configuration file format created by Tom Preston-Werner, aiming to be simpler than YAML and more readable than JSON. TOML 1.0 was officially released in 2021. Core concepts: key-value pairs (key = value), tables ([table]), array of tables ([[array]]), inline tables ({key = value}). TOML supports strings, integers, floats, booleans, datetimes, arrays, and inline tables. Compared to YAML, TOML has no indentation sensitivity issues; compared to JSON, TOML supports comments and is easier to write by hand. Rust's Cargo, Python's pip, and Hugo static site generator all use TOML for configuration.