JSON to TOML

What Is JSON to TOML Conversion?

JSON to TOML conversion transforms data from JavaScript Object Notation into Tom's Obvious Minimal Language. JSON uses curly braces, square brackets, and quoted keys to represent structured data. TOML uses a flat key-value syntax with section headers (called tables) that reads like an INI file but with strict typing. TOML was designed specifically for configuration files where human readability matters more than machine interchange.

TOML has become the default configuration format for Rust (Cargo.toml), Python packaging (pyproject.toml), Hugo static sites, Netlify deployment settings, and many CLI tools. When your source data exists as JSON — from an API response, an exported config, or a generated file — and your target system expects TOML, you need a converter that maps JSON objects to TOML tables, JSON arrays to TOML arrays, and preserves every data type accurately.

Converting JSON to TOML online is the fastest way to generate valid TOML from existing JSON data. The conversion handles type mapping automatically: JSON strings become TOML strings, JSON numbers become TOML integers or floats, JSON booleans map directly, and JSON objects become TOML tables. The one exception is null — TOML has no null type, so null values are either omitted or converted to empty strings depending on the converter.

Why Use This JSON to TOML Converter?

TOML is what config files expect; JSON is what APIs and tools produce. This converter bridges the gap so you can move data between the two formats without manual rewriting.

JSON to TOML Use Cases

JSON vs TOML Comparison

JSON and TOML overlap in capability but differ in syntax, type support, and intended use. This table shows the differences that affect conversion.

TOML Conversion Gotchas

TOML has rules that differ from JSON in ways that affect conversion output. These four issues cause the most confusion.

Code Examples

Converting JSON to TOML programmatically requires a TOML serialization library in most languages. Standard libraries parse JSON; TOML output needs a dedicated package.

import { stringify } from '@iarna/toml'

const json = '{"title":"My App","database":{"host":"localhost","port":5432}}'
const obj = JSON.parse(json)
const toml = stringify(obj)
console.log(toml)
// → title = "My App"
// →
// → [database]
// → host = "localhost"
// → port = 5432

import json
import tomli_w  # pip install tomli_w

json_str = '{"title": "My App", "database": {"host": "localhost", "port": 5432}}'
data = json.loads(json_str)
toml_str = tomli_w.dumps(data)
print(toml_str)
# → title = "My App"
# →
# → [database]
# → host = "localhost"
# → port = 5432

package main

import (
    "encoding/json"
    "fmt"
    "github.com/pelletier/go-toml/v2"
)

func main() {
    jsonStr := `{"title":"My App","database":{"host":"localhost","port":5432}}`
    var data map[string]interface{}
    json.Unmarshal([]byte(jsonStr), &data)

    tomlBytes, _ := toml.Marshal(data)
    fmt.Println(string(tomlBytes))
    // → title = 'My App'
    // →
    // → [database]
    // → host = 'localhost'
    // → port = 5432
}

# Using yj (https://github.com/sclevine/yj)
echo '{"title":"My App","port":3000}' | yj -jt
# → title = "My App"
# → port = 3000

# Using remarshal (pip install remarshal)
echo '{"title":"My App","port":3000}' | remarshal -if json -of toml
# → title = "My App"
# → port = 3000

Frequently Asked Questions