The Short Answer
- JSON: APIs, data exchange, anything machines read
- YAML: Config files that humans edit frequently
- TOML: Simple configs where YAML's indentation is overkill
JSON: The Universal Standard
JSON won the data interchange war. Every language parses it, every API speaks it, every developer knows it.
{
"database": {
"host": "localhost",
"port": 5432,
"name": "myapp"
},
"cache": {
"ttl": 3600,
"enabled": true
}
}Strengths: Universal support, strict syntax (less ambiguity), fast parsing.
Weaknesses: No comments, verbose (lots of quotes and braces), trailing comma errors.
YAML: The Human-Friendly Format
YAML strips away the noise. No quotes around keys, no braces, indentation defines structure.
database:
host: localhost
port: 5432
name: myapp
cache:
ttl: 3600
enabled: trueStrengths: Clean, readable, supports comments, anchors & aliases for DRY configs.
Weaknesses: Indentation sensitivity (tabs vs spaces!), surprising type coercion (yes becomes true), complex spec.
The YAML Gotcha
# What you wrote:
country: NO
# What YAML parsed:
country: false # "NO" is a boolean in YAML 1.1!Always quote strings that could be misinterpreted.
TOML: The Config Sweet Spot
TOML was designed specifically for config files. It's like INI files grew up:
[database]
host = "localhost"
port = 5432
name = "myapp"
[cache]
ttl = 3600
enabled = trueStrengths: Obvious syntax, strong typing, great for flat/shallow configs, no indentation issues.
Weaknesses: Deeply nested structures get awkward, less universal tooling than JSON/YAML.
When to Use Each
| Scenario | Format | Why |
|---|---|---|
| REST API responses | JSON | Universal, fast, typed |
| Kubernetes manifests | YAML | Complex nesting, human-edited |
| Rust/Go project config | TOML | Cargo.toml, go.mod patterns |
| Package metadata | JSON | package.json, composer.json |
| CI/CD pipelines | YAML | GitHub Actions, GitLab CI |
| Simple app settings | TOML | Clean, typed, no surprises |
| Data serialization | JSON | Streaming, parsing speed |
Converting Between Formats
Our Linter tool auto-detects all three formats and can convert between them with one click:
- JSON → YAML (click "Convert" tab)
- YAML → TOML (click "Convert" tab)
- TOML → JSON (click "Convert" tab)
It cycles through the formats: JSON → YAML → TOML → JSON.
You can also validate, format, minify, and flatten any of the three. Try pasting your config and see what happens.
