TOML to JSON Converter

What is TOML and Why Convert to JSON?

// Convert TOML to JSON in Node.js using the smol-toml library
import { parse } from 'smol-toml';

const toml = `
[package]
name = "my-app"
version = "1.0.0"

[dependencies]
serde = { version = "1.0", features = ["derive"] }
`;

const data = parse(toml);
const json = JSON.stringify(data, null, 2);

console.log(json);
// {
//   "package": { "name": "my-app", "version": "1.0.0" },
//   "dependencies": {
//     "serde": { "version": "1.0", "features": ["derive"] }
//   }
// }

Key Features

Examples

[package]
name = "my-app"
version = "1.0.0"
edition = "2021"
authors = ["Jane Doe <jane@example.com>"]

[dependencies]
serde = { version = "1.0", features = ["derive"] }
tokio = { version = "1", features = ["full"] }

[dev-dependencies]
criterion = "0.5"

[[bin]]
name = "my-app"
path = "src/main.rs"

[build-system]
requires = ["hatchling"]
build-backend = "hatchling.build"

[project]
name = "my-package"
version = "0.3.1"
requires-python = ">=3.10"
dependencies = [
  "requests>=2.31",
  "pydantic>=2.0"
]

[project.optional-dependencies]
dev = ["pytest>=8.0", "ruff>=0.4"]

[tool.ruff]
line-length = 100

[build]
command = "npm run build"
publish = "dist"

[build.environment]
NODE_VERSION = "20"

[[redirects]]
from = "/old-path"
to = "/new-path"
status = 301
force = true

[[headers]]
for = "/*"

[headers.values]
X-Frame-Options = "DENY"

baseURL = "https://example.org"
languageCode = "en-us"
title = "My Hugo Site"
theme = "ananke"

[params]
description = "A static site built with Hugo"
mainSections = ["posts", "docs"]

[[menu.main]]
name = "Blog"
url = "/posts/"
weight = 1

[[menu.main]]
name = "About"
url = "/about/"
weight = 2

edition = "2021"
max_width = 100
hard_tabs = false
tab_spaces = 4
newline_style = "Unix"
use_small_heuristics = "Default"
reorder_imports = true
reorder_modules = true

title = "Deployment Log"
last_deployed = 1979-05-27T07:32:00Z
release_date = 1979-05-27
maintenance_window = 02:00:00

[[servers]]
name = "alpha"
ip = "10.0.0.1"
ports = [8001, 8002]

[[servers]]
name = "beta"
ip = "10.0.0.2"
ports = [9001]

How to Use

1. 1

   Paste Your TOML

   Enter or paste your TOML into the input field above. You can also click 'Load example' to try a real Cargo.toml, pyproject.toml, or deployment config.

2. 2

   See Live JSON Output

   JSON appears instantly in the output panel. Adjust the Indent option (2 or 4 spaces) to match your target format. Dates, tables, and arrays of tables are handled automatically.

3. 3

   Copy or Download

   Click Copy to grab the JSON to your clipboard, or Download to save it as a .json file ready for your program, API, or tooling.

Common TOML Pitfalls

name = my-app

name = "my-app"

name = "a"
name = "b"

name = "a"
alt_name = "b"

released = 2026-7-2

released = 2026-07-02

ports = [8001, 8002

ports = [8001, 8002]

snowflake = 1420070400000000000

snowflake = "1420070400000000000"

[servers]
name = "a"
[servers]
name = "b"

[[servers]]
name = "a"
[[servers]]
name = "b"

Common Use Cases

Rust Cargo Metadata

Convert Cargo.toml to JSON to build dependency dashboards, audit crate versions and features, or feed manifest data into scripts and CI that expect JSON rather than TOML.

Python Project Config

Convert pyproject.toml to JSON to inspect PEP 621 project metadata, extract dependency lists, or drive tooling that reads packaging configuration programmatically.

Deployment Config Inspection

Convert netlify.toml, foundry.toml, or other platform configs to JSON to audit redirects, headers, and build settings, or to generate equivalent config for a different platform.

Config Format Migration

Convert TOML application config to JSON when moving to a system that prefers JSON, or as an intermediate step before transforming further with JSON tooling like jq.

Static Site Settings

Convert Hugo config.toml to JSON to migrate site settings, diff configuration across environments, or build a settings UI backed by JSON.

API and Script Input

Turn human-authored TOML into JSON that a REST API, serverless function, or automation script can consume directly, bridging readable config and machine input.

Technical Details

TOML 1.0.0 Parsing via smol-toml

TOML is parsed with the smol-toml library, a zero-dependency, fully TOML 1.0.0-compliant parser. It correctly handles nested tables, dotted keys, inline tables, arrays of tables, multi-line strings, and all four date-time types, and it reports parse errors with line and column positions.

Lossless Date-Time and Safe Integer Handling

TOML date-times are serialized to JSON strings that preserve their exact kind (offset date-time, local date-time, local date, local time). Integers beyond JavaScript's safe range (2^53 - 1) are promoted to BigInt during parsing, then converted to the nearest JSON number with a precision warning, so valid TOML never fails to convert.

100% Browser-Based — No Upload, No Server

All processing happens in your browser's JavaScript engine. No data is transmitted at any point. Inputs larger than 200KB switch from live to manual mode (an explicit Convert click) to keep the interface responsive.

Best Practices

Store Very Large Integers as Strings

If your TOML has integers beyond 2^53 - 1 (Snowflake IDs, nanosecond timestamps, large counters), quote them as strings before converting. JSON numbers in the browser cannot hold them exactly, and the tool will warn you when it has to round.

Prefer 2-Space Indent for JSON Output

Two-space indentation is the most widely used convention for JSON and produces clean, readable output that plays well with most formatters and diff tools. Reserve 4-space indent for when a style guide requires it.

Validate the JSON Output Before Using It

After converting, if you plan to hand-edit the JSON or feed it somewhere strict, run it through our JSON Formatter to confirm it is valid and consistently formatted.

Keep TOML Comments Separately

JSON has no comment syntax, so TOML # comments are dropped on conversion. If the comments are important documentation, keep the original TOML in version control alongside the generated JSON.

Use Arrays of Tables for Repeated Sections

When you have multiple similar sections (servers, redirects, bins), write them as arrays of tables ([[section]]) rather than repeating [section]. They convert to a clean JSON array of objects instead of causing a duplicate-table error.

Frequently Asked Questions