What is YAML?
YAML (YAML Ain’t Markup Language) is a human-friendly data serialization language widely used for configuration files and data exchange. Originally released in 2001, YAML was designed to be easily readable by humans while remaining machine-parseable. It’s used by popular tools like Ansible, Kubernetes, Docker Compose, GitHub Actions, and many other DevOps and CI/CD platforms.
YAML relies on indentation (spaces, not tabs) to denote structure. It supports scalars (strings, numbers, booleans), sequences (arrays/lists), and mappings (key-value pairs/dictionaries). Its clean syntax makes it a popular alternative to JSON and XML for configuration.
What is TOML?
TOML (Tom’s Obvious Minimal Language) was created by Tom Preston-Werner, co-founder of GitHub. TOML is designed to be a minimal configuration file format that is easy to read due to its obvious semantics. It maps unambiguously to a hash table and is used as the default configuration format for Rust’s Cargo package manager, Hugo, and Python’s pyproject.toml.
TOML uses [section] headers (called tables), dot-separated keys, and explicit typing. Unlike YAML, TOML doesn’t rely on indentation for structure — instead it uses explicit table headers and key-value pairs separated by =.
How to Convert YAML to TOML
- Paste your YAML content into the input area
- Click the “To TOML” button or press
Ctrl+Enter - Review the generated TOML output
- Copy the result with the “Copy” button or
Ctrl+Shift+C
To convert in the other direction, paste TOML content and click “To YAML”.
YAML vs TOML Comparison
| Feature | YAML | TOML |
|---|---|---|
| Structure | Indentation-based | Section headers with [] |
| Readability | Very readable for simple data | Very readable for config files |
| Nesting | Via indentation | Via dotted keys or [table] |
| Arrays | - item syntax | ["item"] syntax |
| Comments | # comments | # comments |
| Multi-line strings | Multiple styles (` | , >`) |
| Date/time | Supported | First-class support |
| Common use | Kubernetes, Ansible, CI/CD | Cargo, Hugo, pyproject.toml |
Common Conversion Scenarios
Developers frequently need to convert between YAML and TOML when migrating between tools. For example, moving a project’s configuration from a YAML-based CI system to a TOML-based build system, or converting Hugo front matter from YAML to TOML format.
Understanding the mapping between the two formats helps avoid common pitfalls: YAML’s nested indentation maps to TOML’s dotted keys or table headers, YAML sequences become TOML arrays, and YAML’s flexible string quoting maps to TOML’s more explicit string types.
Tips for Clean Conversions
- Keep your YAML flat when possible — deeply nested YAML produces verbose TOML with many table headers
- Use consistent indentation (2 spaces recommended) in your YAML for reliable parsing
- Be aware that TOML doesn’t support null values — YAML
nullor~will be converted to empty strings - TOML requires explicit quoting for strings that could be misinterpreted as other types
- Both formats support comments with
#, but comments aren’t preserved during conversion