TOML Format Guide

About TOML Format

TOML (Tom's Obvious Minimal Language) is a configuration file format created by Tom Preston-Werner, co-founder of GitHub, in 2013. It was designed to be a minimal, unambiguous configuration format that maps clearly to a hash table. Unlike INI, TOML has a formal specification and supports native data types including strings, integers, floats, booleans, dates/times, arrays, and nested tables.

TOML has been widely adopted in the Rust ecosystem (Cargo.toml), Python packaging (pyproject.toml, Poetry, pip), static site generators (Hugo, Netlify), and many other tools. Its key advantage over YAML is unambiguous parsing — there's only one way to represent each value. Compared to JSON, TOML supports comments and is more human-friendly for configuration. Python 3.11+ includes the tomllib module in the standard library, cementing TOML's status as a first-class configuration format.

Available Conversions

TOML Format Features

• Native Data Types: Strings, integers, floats, booleans, dates/times, arrays, tables
• Formal Specification: Unambiguous grammar with clear parsing rules
• Human-Readable: Minimal syntax designed for easy reading and editing
• Comment Support: Full-line and end-of-line comments with #
• Nesting: Sections via [table], sub-tables via [table.subtable], array of tables via [[array]]
• Inline Tables: Compact notation for small tables: {key = "value"}
• Multiline Strings: Triple-quoted strings for long values

Common Uses

• Rust Ecosystem: Cargo.toml for package management and build configuration
• Python Packaging: pyproject.toml (PEP 518/621), Poetry, pip, setuptools
• Static Site Generators: Hugo front matter, Netlify configuration
• CI/CD: GitHub Actions (partial), various build tool configs
• Application Config: Database settings, server configuration, feature flags
• Development Tools: Black, isort, mypy, ruff, taplo formatter configs
• Infrastructure: Terraform configurations, container settings