TOML Formatter

The TOML Formatter cleans up and pretty-prints TOML documents. Paste in a Cargo.toml, pyproject.toml, or any other TOML config with inconsistent spacing, and get back a canonically formatted version with normalized key = value spacing and consistent table syntax.

What is TOML?

TOML (Tom's Obvious, Minimal Language) is a configuration file format designed to be easy for humans to read and unambiguous for machines to parse. It's the standard config format for a growing list of tools and ecosystems:

• Cargo.toml — Rust package manifests
• pyproject.toml — Python project and build configuration
• .taplo.toml, netlify.toml, wrangler.toml — assorted build/deploy tooling

TOML documents map onto nested key-value structures using [table] headers, [[array-of-tables]] for repeated blocks, inline tables ({ a = 1, b = 2 }), and typed values (strings, integers, floats, booleans, dates, and arrays). Because the grammar allows a lot of stylistic freedom — extra whitespace around =, arbitrary blank lines, an inline table where a full [table] would work just as well — hand-edited TOML tends to drift into an inconsistent mix of styles over time.

How to use it

1. Paste your TOML content into the input box (or click Try an example).
2. The formatted result appears instantly in the output panel, ready to copy or download.
3. Toggle Sort keys alphabetically if you want every table's keys (and top-level tables) reordered A–Z.

What the formatter does

This tool parses your TOML into a value tree and re-serializes it, which canonicalizes:

• Spacing: every pair becomes key = value with exactly one space on each side of =.
• Table syntax: nested objects are always written as [table] / [table.subtable] headers — an inline table like serde = { version = "1.0" } comes back out as its own [dependencies.serde] block, since the parser has no way to remember it was written inline.
• Quoting: strings are re-emitted with consistent, JSON-style escaping.
• Array-of-tables blocks ([[bin]]) are preserved as array-of-tables.

What it does NOT preserve

Because formatting works by fully parsing the document and rebuilding it from the parsed values (not by re-indenting the original text), two things are lost in the round-trip:

• Comments. TOML's grammar treats # comments as insignificant whitespace, so they are not part of the parsed value tree and cannot be re-emitted. If your file has comments you want to keep, keep a copy of the original.
• Original key order is preserved only when "Sort keys" is off — otherwise every table's keys are sorted alphabetically, including the top-level table.

Frequently asked questions

Does formatting change what my config means?

No — every value (string, number, boolean, date, array, table) round-trips to the same value, just re-serialized in a canonical style. Only comments are lost, and only "Sort keys" changes key order.

Why did my { inline = "table" } turn into a [section] block?

The TOML spec allows the same data to be written as either an inline table or a full [table] header — they're equivalent. The underlying parser has no concept of "this was inline," so every nested table comes back out in the full-header form.

Can I control the indentation width?

No — the formatter always writes tables flush-left with no per-depth indentation, which is valid, idiomatic TOML (this is also how cargo fmt-adjacent TOML tooling and most real-world Cargo.toml/pyproject.toml files look). There's no indent-size option to configure.

What happens with invalid TOML?

You'll get a specific error message with the line and column where parsing failed, instead of a blank or broken result.

Is my data private?

Yes. Formatting runs entirely in your browser. Your TOML content is never uploaded to a server.