⌘ K
json → toml · @iarna/toml · tables · arrays · live

Convert JSON to TOML

Turn a JSON object into a TOML configuration. Nested objects become tables, arrays stay arrays, and typed scalars (numbers, booleans) survive intact.

JSON → TOML
Input
162 B
5 lines
Output
0 B
1 lines
Status
loading
parser…
Ratio
0.00×
out/in
input · json
output · toml
Loading parser…
Quick Start

How JSON becomes TOML

The @iarna/toml stringifier walks the JSON tree. Nested objects emit as [section] tables, primitive types pass through, and arrays render as inline lists.

  1. 01

    Paste JSON

    Any object — most commonly a configuration file.

    Parsing runs through Prettier’s standalone bundle (or the language-specific equivalent) loaded lazily — no parser ships until the tool is opened.

    inputPrettierASTstandalonelazy
    in · sourcejson · AST
    { "owner": { "name": "Jane" } }
    loaded · parsedAST · ready
  2. 02

    Tables emit

    Each nested object becomes a [section] header.

    Indent width, tab style, and print-width re-format through a memoised pass — switching 2 → 4 spaces never re-parses, only re-prints.

    tablesindentprint-widthmemoisedlive
    obj · options[sect] · live
    [owner]
name = "Jane"
    options applied · livelive
  3. 03

    Typed scalars

    Numbers, booleans, strings keep their TOML-native form.

    The formatter is deterministic and idempotent: running it twice produces byte-identical output, which keeps diffs and git noise to a minimum.

    typesidempotentdeterministicdiff-cleanstable
    type · formattedpreserve · ready
    enabled = true
    formatted · liveidempotent
  4. 04

    Copy or download

    Drop into Cargo.toml, pyproject.toml or any config file.

    Download writes a Blob with the language-appropriate extension; copy uses navigator.clipboard.writeText so the output preserves all whitespace exactly.

    exportclipboardbloblanguage MIMEclient-side
    ✓ · copiedready · done
    ✓ Copied
    shipped · ready to shipsuccess
Pro tips

Formatting tips that keep diffs sane

Pick one config and pin it

Inconsistent formatting causes diff churn. Commit .prettierrc / .editorconfig and enforce in CI.

Format on save

Editor integration is faster feedback than a pre-commit hook. Use both for belt-and-braces.

Idempotency matters

Running the formatter twice should produce identical output. Test this on a representative file.

Match the language community

Default to community conventions: 2 spaces for JS/CSS, 4 for Python, tabs for Go. Fights over indent are a productivity tax.

Print-width drives wrapping

80, 100, and 120 are the common targets. Wider lines parse fast but review slower side-by-side.

Don’t mix formatters and linters

Prettier handles whitespace; ESLint handles correctness. Disable overlapping rules to avoid fight-club configs.

Related toolsTOML to JSONJSON to XMLJSON to INIJSON to SQLINI to JSONJSON to .env
Use Cases

When to convert JSON to TOML

Rust, Python, config-as-code.

Cargo.toml

Hand-craft a Cargo.toml from JSON dependency lists. Idempotent: running the formatter twice produces byte-identical output, which is the foundation of a clean CI gate. Pair with a pre-commit hook so PRs arrive already formatted, focusing review on logic.

idempotent

pyproject.toml

Generate Python project config from a JSON template. Pairs with EditorConfig + .prettierrc for end-to-end consistency. Whitespace-only changes vanish so reviewers see real diffs, and git blame stays honest about who wrote what.

CI-ready

Config migration

Move JSON config to TOML for readability. Output respects your indent width, tab style, and print-width — settings carry over for repeat runs. Switching 2-space to 4-space costs nothing in CPU but standardises an entire codebase.

diff-clean

Templating

Render TOML from a JSON build step. Format-on-save is the fastest feedback loop; CI is the safety net. Together they make inconsistent indentation a thing of the past and free up review cycles for genuine concerns.

PR-friendly

Hugo / Zola configs

Static site generators that prefer TOML. Whitespace-only changes don't trigger downstream content-hash invalidations, so CDN cache keys and CI cache layers stay warm. Real changes get all the rebuild budget.

review-ready

Project metadata

Cross-system metadata files in TOML form. Pairs with linters (ESLint, Stylelint, pylint) that catch what formatting alone can't — bugs, unused imports, dead code. Each tool stays in its lane, and the codebase stays clean.

deterministic
FAQ

Frequently asked questions

TOML doesn't allow top-level arrays. Wrap them in an object first.
Source comments don't survive round-trips through JSON — TOML output is comment-free.
Strings that look like RFC 3339 are kept as strings. Use TOML datetime literals directly if you need typed dates.
Yes — arrays of objects emit as [[section]] arrays of tables.
No — conversion runs locally in your browser.
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