TOML (Tom's Obvious, Minimal Language) is a human-readable configuration file format created by Tom Preston-Werner, co-founder of GitHub. It's designed to be simpler than YAML and more expressive than INI. TOML supports comments, explicit data types (strings, integers, floats, booleans, dates, arrays, and nested tables), making it ideal for configuration files in Rust (Cargo.toml), Python (pyproject.toml), Go, and many other ecosystems.

TOML offers several advantages over JSON for configuration: comments (JSON doesn't support them natively), better readability with cleaner syntax for nested structures, native date/time types, multi-line strings, and less syntactic noise (fewer quotes and braces). However, JSON remains the standard for data interchange between systems and APIs. This converter bridges both worlds, letting you write configs in TOML and convert to JSON when needed for programmatic use.

This converter supports the full TOML v1.0.0 specification, including: key-value pairs, dotted keys, strings (basic, literal, multi-line), integers (decimal, hex, octal, binary), floats (including scientific notation), booleans, offset date-times, local date-times, local dates, local times, arrays, inline tables, standard tables ([table]), and array of tables ([[array]]). All TOML data types are accurately mapped to their JSON equivalents.

This specific tool focuses on TOML-to-JSON conversion for reliability and accuracy. While JSON-to-TOML conversion is technically possible, it presents challenges: JSON lacks comments, doesn't distinguish between date strings and actual dates, and has no concept of TOML's table types. For reverse conversion, specialized tools exist, but they may require manual adjustments to restore TOML-specific features like comments and proper type inference.

Absolutely. All conversion happens entirely in your browser using client-side JavaScript. Your TOML input is never sent to any server, stored, or logged. The TOML parser (@ltd/j-toml) runs locally. You can verify this by disconnecting your internet after the page loads — the converter will continue to work perfectly. For sensitive configuration files, this ensures complete privacy.

TOML dates and times are converted to ISO 8601 string format in JSON, since JSON has no native date type. For example, 2024-01-15 becomes "2024-01-15", and 14:30:00 becomes "14:30:00". Offset date-times like 2024-01-15T14:30:00+08:00 are preserved with their timezone offset. When consuming the JSON output programmatically, you'll need to parse these strings back into date objects using your language's date parsing functions.

Common scenarios include: CI/CD pipelines that consume JSON configuration; API integrations where a service expects JSON; migrating legacy JSON configs to TOML for better readability while keeping JSON as a fallback; build tool integration (converting Cargo.toml or pyproject.toml metadata to JSON for tooling); and documentation generation where JSON is easier to process programmatically.

Common TOML syntax errors include: duplicate keys (TOML forbids redefining a key in the same table), mixed table types (defining both [a] and [[a]]), invalid date formats, unclosed multi-line strings ("""), and incorrect indentation in arrays. The error message will highlight the exact line and column where the parser encountered the problem. Try loading one of our samples to see valid TOML structure.