TOML Validator
Validate TOML (Tom's Obvious, Minimal Language) configuration file syntax and structure. Check Cargo.toml, pyproject.toml, or any TOML config for parsing errors, analyze tables and keys, and generate detailed reports.
Recommended Settings
For Rust Development
- •Validate Cargo.toml before building projects
- •Check dependency declarations for syntax errors
- •Verify package metadata is properly formatted
For Python Development
- •Validate pyproject.toml before publishing packages
- •Check Poetry/PDM configuration syntax
- •Ensure build system settings are correct
For Configuration
- •Validate before deploying to production
- •Check error messages for specific syntax issues
- •Use validation before converting to other formats
Pro Tips
- •Top-level keys appear before any [table] header
- •Array tables [[name]] allow multiple entries with same structure
- •Validation doesn't check value formats or enforce schemas
- •All validation happens client-side for complete privacy
Most Popular
Most users validate Cargo.toml and pyproject.toml before builds
When to Use This Tool
Validate Rust project Cargo.toml files to identify syntax errors, malformed tables, or invalid key-value pairs before building. Catch parsing issues early to prevent build failures and ensure your dependency declarations are correct.
Recommended: Rust Development
Check Python project pyproject.toml files for Poetry, PDM, or modern pip configurations. Ensure your project metadata, dependencies, and build settings are properly formatted before publishing or deploying your Python packages.
Recommended: Python Development
Validate TOML configuration files to identify syntax errors, duplicate keys, or structural issues before deploying to production. Catch parsing problems early to prevent application crashes or configuration errors in production environments.
Recommended: Config Management
Check TOML file structure and syntax before converting to JSON, XML, or YAML. Ensure your TOML file is properly formatted to avoid conversion errors and data loss. Identify structural issues that might cause problems during format transformation.
Recommended: Data Migration
Analyze TOML configuration files to understand their structure, count tables and keys, and generate reports for documentation or compliance. Useful for configuration management, security audits, and maintaining configuration inventories.
Recommended: Auditing
Test TOML syntax as you learn the format. Experiment with tables, array of tables, nested structures, and data types. Get immediate feedback on syntax errors to understand TOML rules and best practices.
Recommended: Education
How It Works
Paste your TOML configuration file content (Cargo.toml, pyproject.toml, etc.)
Click 'Validate TOML' to parse and analyze
Tool attempts to parse the TOML syntax using @iarna/toml
If valid: displays tables, array tables, keys, and statistics
If invalid: shows specific error messages with details
Review structure breakdown to understand file organization
Copy detailed report for documentation or debugging
100% Private
Files never leave your device. All processing happens locally in your browser.
Lightning Fast
Powered by Client-side JavaScript with '@iarna/toml' parsing library for optimal performance on modern browsers.
Open Source
Built with verified, open-source libraries. Fully transparent.
Frequently Asked Questions
What does the validator check?
The validator parses your TOML file to check for syntax errors, identifies all tables and array of tables, counts configuration elements, and verifies the overall structure. It detects malformed syntax, duplicate keys, invalid table headers, or data type issues.
What are top-level keys?
Top-level keys are key-value pairs that appear before any [table] header in the TOML file. They're placed at the root level of the configuration. For example, 'title = "Config"' before the first [section] is a top-level key. These are similar to global keys in INI files.
What's the difference between tables and array of tables?
Tables use [section] headers and represent single objects. Array of tables use [[section]] headers and represent arrays of objects. For example, [[servers]] allows multiple server entries, while [database] is a single database config. The validator identifies both types.
Does it validate key/value formats?
The validator checks TOML syntax (tables, keys, values, arrays) and data types but doesn't validate against custom schemas. It ensures the file can be parsed correctly but doesn't enforce business rules like 'port must be between 1-65535' or 'email must be valid'.
Can I validate Cargo.toml or pyproject.toml?
Yes! This tool works with any valid TOML file including Cargo.toml (Rust dependencies), pyproject.toml (Python projects), or custom application configs. Just paste the entire file contents to validate syntax and analyze structure.
Can I export the validation report?
Yes! Click 'Copy Report' to copy a formatted text report to your clipboard. The report includes validation status, statistics (table count, key count, array tables), a list of all tables with their keys, and any error messages if validation failed.
What are common TOML errors?
Common errors include: duplicate keys in the same table, invalid datetime formats, unquoted strings with special characters, missing closing brackets, mixing inline tables with regular tables, mismatched array types, and invalid escape sequences in strings.
Is my data safe?
Absolutely! All validation happens entirely in your browser using client-side JavaScript. No data is ever sent to any server, ensuring complete privacy and security for your configuration files including Cargo.toml and pyproject.toml.