TOML Formatter
FormattersFormat and validate TOML with smol-toml. Explore structure in an interactive tree or D3 graph, export as JSON, SVG, or PNG. Ideal for Cargo.toml. Browser-based.
About TOML Formatter
The TOML Formatter is a smol-toml-powered, browser-based tool that parses, validates, and re-serialises TOML configuration files into clean, consistently structured output. It validates documents against the TOML v1.0 specification and surfaces parse errors with precise messages. After formatting, three additional output views are available: a JSON representation of the parsed data, an interactive Tree View for collapsing and expanding sections, and a card-based Graph View that renders the key hierarchy as a hierarchical node graph — exportable as SVG or PNG. All processing happens client-side; your configuration files never leave the browser.
Features
- ✓Powered by smol-toml — a fast, spec-compliant TOML v1.0 parser and serialiser
- ✓TOML v1.0 validation with clear parse error messages
- ✓Formats all TOML types: strings, integers, floats, booleans, dates, arrays, tables
- ✓Handles inline tables, arrays of tables ([[table]]), and dotted key notation
- ✓JSON output tab — view the fully parsed TOML as formatted JSON
- ✓Interactive Tree View — collapse and expand TOML sections by depth
- ✓Interactive Graph View — visualise section and key relationships as a card-based hierarchical graph
- ✓Export graph as SVG (vector, lossless) or PNG (raster, high-resolution)
- ✓Syntax-highlighted editor for both input and output
- ✓One-click clipboard copy of TOML or JSON output
- ✓Real-time byte-savings stats (input vs output size)
- ✓Language picker — instantly switch to JSON, YAML, or 20+ other formatters
- ✓Mobile-responsive layout with a dedicated Format button
- ✓100% client-side — your configuration files never leave the browser
Common Use Cases
- Formatting Cargo.toml workspace and package configurations before committing
- Validating pyproject.toml files for Python packages and Poetry projects
- Exploring complex TOML configuration hierarchies with the tree or graph view
- Converting TOML to JSON for interoperability with JSON-only tooling
- Normalising Helm chart values.toml or custom build configuration files
- Debugging TOML parse errors with precise validation messages
- Reviewing TOML configuration structure in a visual graph before merging
Frequently Asked Questions
QWhich TOML version does this support?
TOML v1.0.0 — the current stable specification, implemented by smol-toml.
QWhat is the JSON output tab?
After formatting, the JSON tab provides the parsed TOML document as a formatted JSON object. This makes it easy to understand the data structure or copy it for use in JSON-only contexts.
QWhat is the Graph View?
The Graph tab renders TOML sections and key relationships as an interactive card-based hierarchical node graph. It can be exported as SVG or PNG for documentation.
QIs my TOML sent to a server?
No. All parsing, formatting, and rendering happens locally inside your browser. Nothing is transmitted to any server.