Is TOML just a simpler YAML?

Not exactly. TOML has a different philosophy: it prioritizes unambiguous parsing and explicit types over minimal syntax. TOML has stronger type safety (distinguishing integers from floats, supporting native dates), while YAML is more flexible with deeper nesting and features like anchors and aliases.

What is the YAML 'Norway problem'?

In YAML 1.1, the bare value NO is interpreted as boolean false instead of the string 'NO'. This caused issues with ISO country codes (Norway = NO) and similar values. YAML 1.2 addressed some cases, but many parsers still exhibit this behavior. TOML avoids this by requiring strings to always be quoted.

Can I convert between TOML and YAML?

Yes. Convertee supports both formats. Convert TOML to JSON first, then JSON to YAML (or vice versa) to move between them. The intermediate JSON step ensures accurate type mapping.

TOML vs YAML: Configuration Format Comparison

Last updated: 2026-04-15

TOML and YAML are both human-friendly configuration formats, but they make different trade-offs. TOML prioritizes simplicity and unambiguous parsing. YAML prioritizes expressiveness and minimal syntax. Picking the right one depends on what you value more: safety or flexibility.

Format Background

TOML

TOML v1.0.0 (Tom's Obvious, Minimal Language) was created by Tom Preston-Werner (co-founder of GitHub). It uses an INI-like syntax with explicit tables, typed values (strings, integers, floats, booleans, dates), and a grammar designed to have exactly one way to represent any given structure.

YAML

YAML 1.2 (YAML Ain't Markup Language) is a data serialization format that uses indentation for structure. It supports complex types including anchors, aliases, and multi-line strings. Its flexibility made it the default for Kubernetes, Docker Compose, GitHub Actions, and Ansible.

Side-by-Side Comparison

Aspect	TOML	YAML
Syntax style	Key-value with `[sections]`	Indentation-based hierarchy
Type safety	Strong (explicit types for dates, integers, floats)	Weak (implicit type coercion can surprise you)
Nesting depth	Flat by design, deep nesting is verbose	Unlimited nesting with indentation
Comments	`#` line comments	`#` line comments
Multi-line strings	Triple-quoted (`"""`)	Block scalars (`\|`, `>`)
Anchors / aliases	Not supported	Supported (DRY config reuse)
Adoption	Rust (Cargo.toml), Python (pyproject.toml), Hugo	Kubernetes, Docker Compose, GitHub Actions, Ansible

Same Config, Two Formats

TOML:

[server]
host = "0.0.0.0"
port = 8080
debug = false

[database]
url = "postgres://localhost/mydb"
pool_size = 5

YAML:

server:
  host: "0.0.0.0"
  port: 8080
  debug: false

database:
  url: "postgres://localhost/mydb"
  pool_size: 5

The YAML "Norway Problem"

YAML 1.1 famously interprets bare NO as a boolean false and 3.14 as a float, even when you meant a string. The ISO country code for Norway (NO) becomes false without quotes. YAML 1.2 fixed some of these cases, but most parsers still default to 1.1 behavior. TOML avoids this entirely: strings are always quoted, numbers always look like numbers.

When to Choose TOML

Application config with flat or shallow structure.
Projects where type safety matters (dates, integers vs. floats).
Rust or Python ecosystems that already use TOML by convention.

When to Choose YAML

Deeply nested config (Kubernetes manifests, CI/CD pipelines).
Configs that benefit from anchors and aliases to reduce duplication.
Ecosystems that already standardize on YAML (DevOps tooling).

Converting Between Formats

Need to switch? Convertee converts between TOML, YAML, and JSON entirely in the browser. See the YAML to JSON and JSON to YAML guides for related workflows.

Frequently Asked Questions

Is TOML just a simpler YAML?: Not exactly. TOML has a different philosophy: it prioritizes unambiguous parsing and explicit types over minimal syntax. TOML has stronger type safety (distinguishing integers from floats, supporting native dates), while YAML is more flexible with deeper nesting and features like anchors and aliases.
What is the YAML 'Norway problem'?: In YAML 1.1, the bare value NO is interpreted as boolean false instead of the string 'NO'. This caused issues with ISO country codes (Norway = NO) and similar values. YAML 1.2 addressed some cases, but many parsers still exhibit this behavior. TOML avoids this by requiring strings to always be quoted.
Can I convert between TOML and YAML?: Yes. Convertee supports both formats. Convert TOML to JSON first, then JSON to YAML (or vice versa) to move between them. The intermediate JSON step ensures accurate type mapping.