DevBolt
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How do I convert TOML to JSON or YAML online?

Paste your TOML content (e.g., Cargo.toml, pyproject.toml) and instantly convert it to JSON or YAML. You can also convert JSON or YAML back to TOML. The tool handles nested tables, arrays of tables, and inline tables. Everything runs in your browser.

TOML to JSON
Input
[package]
name = "my-app"
version = "1.0.0"
edition = "2021"

[dependencies]
serde = "1.0"
tokio = { version = "1", features = ["full"] }
Output
{
  "package": {
    "name": "my-app",
    "version": "1.0.0",
    "edition": "2021"
  },
  "dependencies": {
    "serde": "1.0",
    "tokio": { "version": "1", "features": ["full"] }
  }
}
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TOML ↔ JSON/YAML Converter

Convert between TOML, JSON, and YAML formats. Perfect for Cargo.toml, pyproject.toml, and configuration files.

About TOML ↔ JSON/YAML Conversion

  • TOML(Tom's Obvious Minimal Language) — simple config format used by Cargo (Rust), pyproject.toml (Python), Hugo, and many CLI tools.
  • JSON — strict key-value format for APIs, data exchange, and tooling configs like package.json and tsconfig.json.
  • YAML — indentation-based format popular for Kubernetes, Docker Compose, and CI/CD pipelines.
  • TOML requires a table (object) at the root — arrays and primitives are not valid top-level values.
  • Everything runs in your browser — no data is sent over the network.

Tips & Best Practices

Pro Tip

TOML preserves data types that JSON and YAML handle differently

TOML natively supports dates (2024-01-15), times, and datetimes without string wrapping. When converting to JSON, these become strings. When converting to YAML, datetime support varies by parser. Be aware of type fidelity when round-tripping between formats.

Common Pitfall

TOML tables and arrays of tables have non-obvious syntax

[server] is a table (object). [[server]] is an array of tables (array of objects). Confusing these causes silent data corruption — your config ends up with one object instead of an array, or vice versa. Double brackets = array.

Real-World Example

pyproject.toml is now the standard Python config format

Python's ecosystem has consolidated on pyproject.toml (PEP 621, PEP 660). Tools like Poetry, Hatch, PDM, Ruff, Black, and pytest all read from it. If you're maintaining Python packages, learning TOML syntax is no longer optional.

Security Note

Validate TOML configs before deployment — syntax errors fail silently

Unlike JSON which fails loudly on parse errors, many TOML parsers silently ignore malformed sections or fall back to defaults. A typo in your Cargo.toml or pyproject.toml could mean missing dependencies or wrong build settings in production.

Frequently Asked Questions

What is TOML and how does it differ from JSON and YAML?
TOML is a configuration format designed for clarity with unambiguous semantics. Unlike JSON, TOML supports comments, has native date/time types, and does not require quotes around most keys. Unlike YAML, TOML avoids indentation-based nesting, eliminating parsing errors. TOML uses [section] headers and dot-separated keys. It is standard for Rust's Cargo.toml, Python's pyproject.toml, and Hugo's config.toml. DevBolt converts bidirectionally between TOML, JSON, and YAML.
How do I convert between TOML, JSON, and YAML?
Paste content in any of the three formats and select the target. The converter maps data types appropriately across formats. TOML datetime values become ISO 8601 strings in JSON. Inline tables expand into standard objects. Comments are lost when converting to JSON since JSON has no comment syntax. All conversion runs in your browser for privacy.
When should I use TOML instead of YAML?
Use TOML when config is relatively flat, you want unambiguous parsing without type coercion surprises, and your ecosystem expects it (Rust, Python packaging, Hugo). TOML's explicit syntax means '123' is always a number and 'true' is always a boolean, unlike YAML where country codes and yes/no values can be misinterpreted. Use YAML for deeply nested structures, anchors/aliases, or when tools require it (Kubernetes, Docker Compose, GitHub Actions).

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