TOML ↔ YAML Converter
Live bidirectional conversion between TOML and YAML.
TOML
YAML
TOML vs YAML — The Bottom Line
Use TOML when you want explicit, unambiguous configuration with native date types and clear section structure — perfect for Cargo.toml, pyproject.toml, and Rust/Python tooling. Use YAML when working in ecosystems that have standardized on it (Kubernetes, Docker Compose, GitHub Actions, Ansible) or when you need anchors/aliases for config reuse.
Side-by-Side Example
TOML
toml
[server]
host = "localhost"
port = 8080
debug = true
[database]
url = "postgresql://localhost/mydb"
max_connections = 10
[[worker]]
name = "default"
concurrency = 4
[[worker]]
name = "email"
concurrency = 2YAML
yaml
server:
host: localhost
port: 8080
debug: true
database:
url: postgresql://localhost/mydb
max_connections: 10
worker:
- name: default
concurrency: 4
- name: email
concurrency: 2Detailed Comparison
| Feature | TOML | YAML |
|---|---|---|
| Syntax style | INI-like sections, explicit types | Indentation-based, minimal punctuation |
| Comments | # line comments | # line comments |
| Multi-line strings | """triple quoted""" | | (literal) or > (folded) blocks |
| Dates | Native ISO 8601 type | String (with type coercion in v1.1) |
| Arrays | Mixed syntax: [] and [[table]] | - list items or [inline] |
| Ambiguity | Very low — explicit and unambiguous | Can be tricky (NO, yes, 0755 gotchas) |
| Spec complexity | Simple (TOML v1.0 is ~3500 words) | Complex (YAML v1.2 is ~100+ pages) |
| Anchors / aliases | Not supported | Yes — &anchor and *alias |
| Schema | No official schema language | Limited (YAML Schema, Ajv-based) |
| Human writability | Easy for structured data | Excellent for simple configs |
| Ecosystem — Rust | Native (Cargo.toml) | Rare |
| Ecosystem — Python | Standard (pyproject.toml) | Django, Ansible, some CI |
| Ecosystem — DevOps | Hugo, Deno | Kubernetes, Docker, GitHub Actions |
TOML Type System
TOML has a rich, explicit type system with native support for dates and times:
toml
# Strings
name = "John Doe"
multiline = """
Line one
Line two
"""
# Numbers
port = 8080
pi = 3.14159
hex = 0xDEADBEEF
# Booleans (always lowercase)
debug = true
verbose = false
# Dates (ISO 8601 native type)
created = 1979-05-27T07:32:00Z
birthday = 1979-05-27
# Arrays
tags = ["rust", "toml", "config"]
# Inline tables
point = { x = 1, y = 2 }YAML Gotchas to Watch Out For
yaml
# YAML 1.1 gotchas (older parsers)
country: NO # "NO" is a boolean false!
mode: 0755 # parsed as octal 493, not 755
on: true # "on" is a boolean true
yes: true # "yes" is also boolean
# Fix: use quotes
country: "NO"
mode: "0755"
# YAML indentation is meaningful
key:
nested: value # child of key
another: value # also child of key
# Anchors and aliases (TOML has no equivalent)
defaults: &defaults
timeout: 30
retries: 3
production:
<<: *defaults # merge defaults
timeout: 60 # overrideMost of the YAML gotchas come from YAML 1.1 parsers (used in older tools). YAML 1.2 (supported by newer tools like yq, PyYAML 6+) is much more strict and eliminates most of these edge cases.
When to Use TOML
- Rust projects — Cargo.toml is the standard; the entire Rust ecosystem uses TOML
- Python packaging — pyproject.toml (PEP 517/518/621) is the modern Python standard
- Hugo static sites — config.toml is Hugo's primary configuration format
- Simple, explicit configs — when you want no surprises and unambiguous parsing
- Date-heavy configs — TOML has native date/time types; YAML treats them as strings
When to Use YAML
- Kubernetes manifests — deployment.yaml, service.yaml, ingress.yaml — the entire K8s ecosystem uses YAML
- Docker Compose — docker-compose.yml is the standard format
- GitHub Actions / GitLab CI — .github/workflows/*.yml and .gitlab-ci.yml
- Ansible playbooks — YAML is central to Ansible's DSL
- Config reuse with anchors — when you need to DRY up config with &anchors and *aliases