Free TOML to JSON Schema Converter — generate a JSON Schema from TOML in your browser

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📐 TOML to JSON Schema — Free Online Tool

Convert TOML to JSON Schema online, free. TOML is a readable configuration format built around key/value pairs and tables. JSON Schema is a vocabulary for validating and documenting the shape of JSON data. TOML to JSON Schema conversion parses your TOML against the TOML v1.0.0 grammar (https://toml.io/en/v1.0.0), builds an in-memory model of its keys, nested objects and arrays, then derives a JSON Schema that describes that shape following the JSON Schema 2020-12 conventions. Processing runs in your browser in JavaScript with no upload or server round-trip — no size limit beyond your device's memory, so multi-megabyte documents convert in milliseconds and sensitive payloads never leave your machine. Typical uses include API request/response validation, form generation and contract testing.

🚀 Why use this TOML to JSON Schema tool?

It maps the full structure of your TOML onto a valid JSON Schema, following the JSON Schema 2020-12 conventions. 100% free, no registration, and complete privacy — everything runs locally in your browser, so your data never touches a server.

Key Features

Instant, in-browser

Paste TOML and derive a JSON Schema from JSON Schema immediately. Conversion runs client-side, so there is no upload wait and large documents stay fast.

🧩Structure-aware mapping

Nested TOML objects, tables and arrays are mapped faithfully onto JSON Schema.

🔒100% private

Your TOML never leaves your device — everything is processed locally in JavaScript, with nothing logged or stored.

🆓Free, no signup

Unlimited conversions with no account, no quotas, and no watermark. Works on desktop and mobile.

Popular Use Cases

Contract & validation

  • Derive a JSON Schema from real TOML
  • Validate future payloads against it
  • Document the expected shape

API request/response validation

  • API request/response validation
  • form generation
  • contract testing

Codegen pipeline

  • Feed the JSON Schema into stub/codegen tools
  • Standardize message shapes
  • Share a single source of truth

What It Handles

Structure

  • Nested objects & tables
  • Arrays / lists
  • Deeply nested documents

Values

  • Inferred types (string, number, boolean)
  • Optional / nullable fields
  • Nested type names

Workflow

  • Copy or download output
  • Load an example to try it
  • Validate & format the input

Worked example

A TOML document and its JSON Schema equivalent:

TOML input:

host = "db.internal"
port = 5432
secure = true

Output:

{
  "type": "object",
  "properties": {
    "host": { "type": "string" },
    "port": { "type": "integer" },
    "secure": { "type": "boolean" }
  },
  "required": ["host", "port", "secure"]
}

Sources & References

Frequently Asked Questions

How do I convert TOML to JSON Schema?

Paste your TOML into the editor and press "Convert to JSON Schema". The tool parses it against the TOML v1.0.0 grammar, then derives a JSON Schema following JSON Schema 2020-12 conventions — instantly and entirely in your browser. You can validate or format the TOML first to be sure it is clean.

How is TOML structure represented in JSON Schema?

TOML values are typed and it has first-class dates and times, so they carry into JSON Schema cleanly. TOML tables become nested JSON Schema structures, and arrays-of-tables become lists.

What does the generated JSON Schema capture?

The derived JSON Schema records the required keys and the value type of each field seen in your TOML sample. Widen it by hand if some fields are optional or can hold more than one type.

What is the difference between TOML and JSON Schema?

TOML (Tom's Obvious Minimal Language) (TOML) — TOML is a readable configuration format built around key/value pairs and tables. JSON Schema (JSON Schema) — JSON Schema is a vocabulary for validating and documenting the shape of JSON data. This converter maps the structure of your TOML onto JSON Schema so you can use it for API request/response validation.

Does the converter validate my TOML first?

Yes. Invalid TOML is flagged with a clear error before anything is converted. Common TOML problems to check are correct key/value pairs, quoted strings, and valid [table] headers. Starting from clean input keeps the generated JSON Schema accurate.

Is my TOML data private?

Yes. The entire TOML-to-JSON Schema conversion runs locally in your browser in JavaScript — your TOML is never uploaded, logged or stored. That matters when the data is something like Rust Cargo & Python pyproject config, which should not leave your machine.

Where can I use the JSON Schema output?

The generated JSON Schema is ready for API request/response validation, form generation and contract testing. Copy or download it and drop it straight into your validation or codegen pipeline.

🎓 Pro Tips

  • Tip 1: Validate or format your TOML first (the Validate / Format buttons) so the converter works from clean, TOML v1.0.0-conformant input.
  • Tip 2: Keep an eye on type coercion: TOML and JSON Schema don't always represent numbers, dates and nulls the same way.
  • Tip 3: Authoritative reference for the input format: TOML v1.0.0 — https://toml.io/en/v1.0.0.
  • Tip 4: For the output, follow the JSON Schema 2020-12 (https://json-schema.org/) conventions in your codebase.