Guide: TOML Formatter & Validator
↑ Back to toolWhat is this tool?
This TOML formatter and TOML validator runs in your browser. Paste TOML (Tom's Obvious, Minimal Language)—valid configs are pretty-printed on the right as you type; parse errors show in the status area. It uses a standard TOML parser; your text is not uploaded to a server. No sign-up.
Use it as an online TOML formatter for snippets, Cargo.toml, pyproject.toml, CI configs, and any file that must be valid TOML before you commit or share.
💡 Quick tip
Keep a copy of files that rely on comments—formatting rewrites TOML and comments are not preserved.
Why TOML?
TOML is a common choice for human-readable configuration: explicit tables, clear nesting, and less ambiguity than YAML for many teams. It appears in Rust (Cargo.toml), Python packaging (pyproject.toml), static sites, Netlify, Poetry, and more. A format TOML online workflow helps you catch typos and structure issues before they land in a repo.
Features
- Live format & validate — Debounced parse; formatted output updates as you edit; invalid TOML surfaces a clear error message.
- Monaco editor — Syntax-aware editing consistent with other Spoold formatters.
- Copy output — One click to copy the formatted result.
- History — Reopen recent sessions from the tool history panel when enabled.
- Client-side — Parsing and formatting happen in your browser.
How to use
- Open the tool — Paste TOML in the input panel or start from the sample.
- Edit — Adjust keys, tables, and values; the formatted preview tracks your changes.
- Check status — Green means valid; red means a parse error to fix in the source.
- Copy — Use copy on the output panel when you are ready to paste elsewhere.
Use cases
| Scenario | How this tool helps |
|---|---|
| Rust / Cargo | Normalize Cargo.toml layout and catch syntax mistakes. |
| Python packaging | Validate and pretty-print pyproject.toml sections. |
| CI & deploy configs | Quick-check TOML before pasting into pipelines or docs. |
| Teaching & snippets | Show clearly indented examples for blog posts or READMEs. |
Best practices
- Back up commented files — Formatting drops inline comments (see limitations).
- Fix errors at the source — The tool highlights parse failures; correct the input, not the preview alone.
- Very large files — The browser may slow down; consider splitting or using a local editor for huge monoliths.
JSON & TOML workflows
This page is TOML-only (format & validate). For JSON, use the JSON Formatter; for JSON ↔ YAML, use JSON ↔ YAML; for two-way JSON ↔ TOML, use JSON ↔ TOML.
Limitations
Formatting re-parses and stringifies TOML. Inline comments and whitespace outside string values are not preserved—keep a backup if comments matter. Very large files may feel slow in the browser.
FAQ
Is this TOML formatter free?
Yes. It runs client-side in your browser with no sign-up.
Does format preserve comments?
No. The formatter parses TOML to a data structure and writes it again, which drops comments. Keep a copy if you need annotations.
Is this a TOML linter for style rules?
It validates syntax and pretty-prints. It does not enforce project-specific naming or ordering rules like a dedicated linter might.
Can I convert TOML to JSON here?
Not on this page—only format and validate TOML. Use the JSON ↔ TOML converter for two-way conversion, or JSON Formatter for JSON-only work.
Does it work offline?
After the app loads, formatting runs in your browser without sending your text to Spoold servers.
Related terms
People often search for toml formatter, toml validator, format toml online, toml pretty print, cargo toml format, pyproject toml validator, toml beautifier, and validate toml online. This tool covers formatting and syntax validation in one place.
Similar tools
Other Spoold utilities you might use alongside TOML:
Conclusion
Use this TOML formatter and validator to pretty-print and check config files in the browser. Pair it with JSON, JSON ↔ YAML, JSON ↔ TOML, or XML when your stack mixes formats.