Validate TOML Online for Free (no login)

TOML (Tom's Obvious, Minimal Language) is the config format behind Rust's Cargo.toml, Hugo sites, Python's pyproject.toml, and dozens of other modern tools — but even small syntax errors can break your build silently. Paste your TOML into the validator below and get instant feedback: line numbers, error descriptions in plain English, and a clear pass/fail result. No install, no sign-up, no file size limit.

How to Validate TOML

1. Paste your TOML — Copy the contents of your .toml file and paste it into the editor, or type directly.
2. Click "Validate" — The tool parses your TOML using a JavaScript parser running entirely in your browser.
3. Review the results — If there are errors, you'll see the exact line number and a plain-English explanation of what went wrong.
4. Fix and re-validate — Correct the issue in the editor and click Validate again until you get a green "Valid TOML" result.
5. Copy the cleaned TOML — Use the copy button to grab your validated TOML and paste it back into your project.
   
   

Why Use Flipper File to Validate TOML?

• Instant feedback — Results appear in under a second with no page reload required.
• Line-by-line error reporting — Know exactly which line is broken and why, not just "parse error."
• Runs entirely in your browser — Your config data never leaves your machine. Perfect for secrets, API keys, and private project settings.
• Works with any TOML file — Cargo.toml, pyproject.toml, Hugo config.toml, Gitea config, TOML-based app configs — all supported.
• Free, no login, no limits — Paste any size config file without creating an account or hitting a paywall.
• Clean, distraction-free interface — No ads, no popups, just your TOML and a clear result.
  
  

Frequently Asked Questions

What is TOML?

TOML stands for Tom's Obvious, Minimal Language. It's a configuration file format designed to be easy for humans to read and write. It's widely used in the Rust ecosystem (Cargo.toml), Python packaging (pyproject.toml), Hugo static site generator (config.toml), and many other modern tools.

Why does my TOML fail to parse?

The most common TOML errors are: missing quotes around strings, incorrect date/time formatting, duplicate keys in the same table, using tabs instead of proper indentation inside inline tables, or mismatched brackets in arrays. This validator will point you to the exact line and describe the problem.

Is my data safe when I use this validator?

Yes. The TOML parser runs entirely in your browser using JavaScript. Your config data — including any API keys, passwords, or credentials — is never uploaded to any server. Everything stays on your device.

Does this tool support the full TOML spec?

The validator supports the TOML v1.0 specification, which covers all standard types: strings, integers, floats, booleans, datetimes, arrays, and tables (including inline tables and array-of-tables).

What's the difference between TOML and JSON?

TOML is designed to be more human-readable than JSON. It supports comments (JSON does not), has more natural multi-line strings, and uses a cleaner syntax for nested sections using [header] notation instead of nested braces. Both formats describe the same underlying data structures.

Can I use this to validate Cargo.toml files?

Absolutely. Cargo.toml is a standard TOML file and this tool will validate its syntax completely. Note that this validator checks TOML syntax, not Cargo-specific field requirements (like valid crate names or version constraints).

What is pyproject.toml?

pyproject.toml is the modern Python packaging configuration file defined by PEP 517/518. It replaced setup.py and setup.cfg in many modern Python projects. This validator will catch any syntax errors in it.

Can I validate TOML on mobile?

Yes. The tool is fully responsive and works on phones and tablets. The code editor is touch-friendly.