TOML vs YAML vs JSON: Choosing the Right Config Format

Compare TOML, YAML, and JSON configuration formats. Learn when to use each format and how to convert between them.

2026-01-087 min

Use the tool alongside this guide for hands-on practice.

What is TOML?

TOML (Tom's Obvious Minimal Language) is a configuration file format created by Tom Preston-Werner, co-founder of GitHub. It aims to be minimal and obvious, making it easy to read and write.

TOML has become the standard configuration format for Rust (Cargo.toml) and Python (pyproject.toml), and is used by many other tools and frameworks.

TOML vs YAML vs JSON comparison

Each configuration format has distinct strengths and weaknesses. Understanding these helps you choose the right format for your project.

TOML: Explicit syntax, no whitespace sensitivity, supports comments, great for config files
YAML: Human-friendly, supports complex structures, whitespace-sensitive (error-prone)
JSON: Universal interchange format, strict syntax, no comments, verbose for config

When to use TOML

TOML excels for application configuration where readability and explicit syntax matter. Its lack of whitespace sensitivity makes it less error-prone than YAML.

Package manifests (Cargo.toml, pyproject.toml)
Application configuration files
CI/CD configuration (netlify.toml, hugo.toml)
Settings that humans will edit frequently

When to use YAML

YAML is ideal for complex nested configurations and data serialization where its features like anchors and aliases provide value.

Kubernetes manifests and Helm charts
Docker Compose files
CI/CD pipelines (GitHub Actions, GitLab CI)
Complex data structures with references

When to use JSON

JSON is the standard for data interchange between systems. Use it when your configuration needs to be consumed by APIs or generated programmatically.

API responses and requests
package.json and similar manifests
Machine-generated configuration
Cross-language data exchange

Converting between formats

Converting between TOML, YAML, and JSON is straightforward since they all represent similar data structures. However, some features are format-specific.

Comments are lost when converting to JSON
YAML anchors/aliases cannot be represented in TOML or JSON
TOML dates become strings in JSON
Nested structures may look different after conversion

TOML syntax quick reference

TOML uses a simple key-value syntax with tables for grouping related settings. Square brackets define table headers, and double brackets create arrays of tables.

FAQ

Is TOML better than YAML?

TOML and YAML serve different needs. TOML is simpler and less error-prone (no whitespace sensitivity), making it better for config files humans will edit. YAML is more powerful for complex nested data but requires more care.

Can I use TOML for Kubernetes?

Kubernetes natively uses YAML. While you could convert TOML to YAML, it's better to use YAML directly for Kubernetes manifests to maintain compatibility with the ecosystem.

Why does Rust use TOML?

Rust chose TOML for Cargo because it's unambiguous and explicit. Unlike YAML, TOML doesn't have whitespace sensitivity issues, and unlike JSON, it supports comments and is more human-readable.

How do I validate a Cargo.toml file?

Use our TOML formatter to paste your Cargo.toml content. It will validate the syntax and highlight any errors. You can also format it for consistent styling.

January 6, 20265 min