TOML to JSON Converter Complete Guide 2026

What is TOML?

TOML (Tom's Obvious, Minimal Language) is a configuration file format designed to be easy to read and write. It uses a simple INI-like syntax with support for nested tables, arrays, and various data types. TOML has become the preferred format for modern tools like Rust's Cargo, Python's Poetry, and static site generators like Hugo.

Why Convert TOML to JSON?

Converting TOML to JSON is essential when you need to:

• Use configuration in web applications — JSON is natively supported in JavaScript
• Exchange data between services — JSON is the standard API format
• Import TOML data into NoSQL databases — Many use JSON-like document formats
• Process configuration with tools that only support JSON
• Validate TOML structure — JSON validators are more widely available

How to Convert TOML to JSON

Method 1: Online TOML to JSON Converter (Fastest)

For quick conversions, use an online TOML to JSON converter:

1. Copy your TOML content
2. Paste into the converter input field
3. Click "Convert" to see the JSON output
4. Copy the result or download as a file

Method 2: Python (tomllib + json)

Python 3.11+ includes built-in TOML support:

import tomllib
import json

# Read TOML file
with open('config.toml', 'rb') as f:
    toml_data = tomllib.load(f)

# Convert to JSON
json_output = json.dumps(toml_data, indent=2)
print(json_output)

# Or save to file
with open('config.json', 'w') as f:
    json.dump(toml_data, f, indent=2)

Method 3: Node.js (toml package)

const fs = require('fs');
const toml = require('toml');

// Read and parse TOML
const tomlContent = fs.readFileSync('config.toml', 'utf8');
const jsonObj = toml.parse(tomlContent);

// Convert to JSON
const jsonOutput = JSON.stringify(jsonObj, null, 2);
console.log(jsonOutput);

// Save to file
fs.writeFileSync('config.json', jsonOutput);

TOML vs JSON: Key Differences

TOML Data Type Mapping

When converting TOML to JSON, data types map as follows:

Basic Types

# TOML
title = "Example"      →  "title": "Example"
count = 42             →  "count": 42
pi = 3.14159           →  "pi": 3.14159
enabled = true         →  "enabled": true
date = 2026-03-10      →  "date": "2026-03-10" (as string)

Arrays

# TOML
numbers = [1, 2, 3, 4, 5]

# JSON
"numbers": [1, 2, 3, 4, 5]

Tables (Objects)

# TOML
[database]
server = "localhost"
port = 5432

# JSON
"database": {
  "server": "localhost",
  "port": 5432
}

Nested Tables

# TOML
[server.connection]
host = "127.0.0.1"
port = 8080

[server.security]
ssl = true
cert = "/path/to/cert"

# JSON
"server": {
  "connection": {
    "host": "127.0.0.1",
    "port": 8080
  },
  "security": {
    "ssl": true,
    "cert": "/path/to/cert"
  }
}

Common Use Cases

1. Rust Cargo to Web App Configuration

Convert Cargo.toml to JSON for use in a web dashboard:

# Cargo.toml (TOML)
[package]
name = "my-app"
version = "1.0.0"
edition = "2021"

[dependencies]
serde = "1.0"
tokio = "1.0"

# Converted JSON
{
  "package": {
    "name": "my-app",
    "version": "1.0.0",
    "edition": "2021"
  },
  "dependencies": {
    "serde": "1.0",
    "tokio": "1.0"
  }
}

2. Poetry (Python) to CI/CD Pipeline

Convert pyproject.toml for use in CI/CD scripts:

# pyproject.toml
[tool.poetry]
name = "my-project"
version = "0.1.0"

[tool.poetry.dependencies]
python = "^3.9"
requests = "^2.28.0"

# JSON for CI/CD
{
  "tool": {
    "poetry": {
      "name": "my-project",
      "version": "0.1.0",
      "dependencies": {
        "python": "^3.9",
        "requests": "^2.28.0"
      }
    }
  }
}

3. Hugo Config to Headless CMS

Convert Hugo's config.toml for import into a CMS:

# config.toml
baseURL = "https://example.com"
languageCode = "en-us"
title = "My Blog"

[params]
  description = "A tech blog"
  author = "John Doe"

# JSON for CMS import
{
  "baseURL": "https://example.com",
  "languageCode": "en-us",
  "title": "My Blog",
  "params": {
    "description": "A tech blog",
    "author": "John Doe"
  }
}

Libraries for TOML to JSON Conversion

Python

• tomllib (Python 3.11+, built-in) — Recommended
• tomli (Python 3.7+, read-only)
• toml (legacy, read/write)

Node.js

• toml — Popular, well-maintained
• @iarna/toml — Fast, supports TOML 1.0
• fast-toml — Performance-focused

Go

• github.com/BurntSushi/toml — Official, recommended
• github.com/pelletier/go-toml — Fast, feature-rich

Rust

• toml — Official crate
• toml_edit — For editing while preserving formatting

Best Practices

1. Validate before converting — Ensure TOML is valid to avoid errors
2. Preserve data types — Don't convert numbers to strings unnecessarily
3. Handle dates carefully — TOML datetime may need special handling in JSON
4. Use pretty-printing — Format JSON output for readability
5. Test round-trip conversion — Convert TOML→JSON→TOML to verify integrity

Common Errors and Solutions

Error: "Invalid TOML syntax"

Cause: Malformed TOML (missing quotes, invalid characters)

Solution: Use a TOML validator or linter before conversion

Error: "Unsupported data type"

Cause: TOML datetime or local time in JSON

Solution: Convert to ISO 8601 string format

Error: "Nested tables not converting"

Cause: Incorrect TOML table syntax

Solution: Ensure proper [parent.child] syntax for nested tables

Frequently Asked Questions

Is TOML better than JSON for configuration?

Yes, for human-editable configuration. TOML supports comments, has cleaner syntax for nested structures, and doesn't require quotes on keys. However, JSON is better for programmatic data exchange.

Can I convert JSON back to TOML?

Yes! Our converter supports bidirectional conversion. JSON to TOML is useful when you want to make configuration files more human-readable.

What's the file size difference?

TOML files are typically 20-30% smaller than equivalent JSON because TOML doesn't require quotes on keys and uses a more compact syntax.

Does the converter preserve comments?

No, JSON doesn't support comments. If you need to preserve comments, keep a backup of the original TOML file.

Related Resources

• JSON Formatter & Validator
• YAML to JSON Converter
• YAML to JSON Complete Guide
• XML to JSON Complete Guide