JSON to TOML
Free online JSON to TOML converter. Convert JSON objects into TOML configuration format. Useful for creating Cargo.toml, pyproject.toml, and other TOML config files.
How to Use JSON to TOML
Paste Your JSON
Paste JSON data into the input panel. The JSON should be a valid object (not an array at the root, since TOML requires a table structure at the top level).
Convert to TOML
Click "JSON to TOML" to transform your data into TOML format. Nested objects become TOML tables (with [header] notation) and arrays become TOML arrays.
Copy and Use
Copy the TOML output for use in configuration files — Cargo.toml (Rust), pyproject.toml (Python), or any TOML-compatible tool.
Example
JSON
{
"project": {
"name": "my-app",
"version": "1.0.0",
"dependencies": {
"express": "4.18.0",
"lodash": "4.17.21"
}
}
}TOML
[project]
name = "my-app"
version = "1.0.0"
[project.dependencies]
express = "4.18.0"
lodash = "4.17.21"Frequently Asked Questions
What is TOML used for?
TOML (Tom's Obvious, Minimal Language) is a configuration file format designed to be easy to read and write. It's the standard config format for Rust projects (Cargo.toml), Python projects (pyproject.toml), and is supported by many other tools. It's like JSON but with comments, cleaner syntax for nested data, and better human readability.
Are there limitations to this conversion?
The conversion handles objects, arrays, strings, numbers, booleans, and null values. The JSON root should be an object (TOML requires a root table). Very deeply nested structures may produce deeply nested TOML table headers, which can become hard to read — but they will be valid TOML.
Does this support all TOML features?
The converter outputs a clean subset of TOML: key-value pairs, arrays, inline tables for simple nested objects, and [table] headers for deeper nesting. It does not generate TOML arrays of tables ([[array]]) since the input JSON doesn't carry enough information to determine when to use that syntax. The output is valid TOML that any TOML parser can read.
Why TOML for Configuration
TOML was created specifically because JSON, YAML, and INI each have drawbacks as configuration formats. JSON lacks comments — a dealbreaker for config files where you want to explain why a setting has a particular value. YAML's indentation-based syntax leads to subtle errors. INI is too simple for nested data.
TOML hits a sweet spot: it supports comments, has a clear specification, handles nesting with a readable [section] syntax, and uses explicit types (unlike YAML, where 1.0 and 1 can behave differently depending on the parser). If you're starting a new project and need a config file format, TOML is worth considering.