JSON to TOML Config Format Converter — Free Online Tool
Convert JSON to TOML configuration format using AI. Produces clean TOML with correct sections, arrays of tables, and inline tables for nested objects. Free, no sign-up.
JSON to TOML Config Format Converter — Free Online Tool
About JSON to TOML Config Format Converter — Free Online Tool
JSON to TOML converts your JSON data into TOML (Tom's Obvious Minimal Language) config format, which is designed for human-readable configuration files. Developers use it when migrating project configs to tools like Cargo, Hugo, or Poetry that require TOML, or when they prefer TOML's explicit typing and section-based structure over JSON's bracket-heavy syntax.
JSON to TOML Type Mapping
| JSON Type | JSON Example | TOML Output | TOML Type |
|---|---|---|---|
| String | "hello" | key = "hello" | Basic string |
| Integer | 42 | key = 42 | Integer |
| Float | 3.14 | key = 3.14 | Float |
| Boolean | true | key = true | Boolean |
| Null | null | Not supported — omit key or use empty string | No native null |
| Array of strings | ["a", "b"] | key = ["a", "b"] | Array |
| Array of objects | [{"x":1}] | [[key]]\nx = 1 | Array of tables |
| Nested object | {"db": {"port": 5432}} | [db]\nport = 5432 | Table / section |
| ISO date string | "2024-01-15T00:00:00Z" | key = 2024-01-15T00:00:00Z | Offset Date-Time |
TOML vs JSON vs YAML for Config Files
| Feature | TOML | JSON | YAML |
|---|---|---|---|
| Human readability | High — flat key=value | Medium — verbose braces | High — indent-based |
| Comments | Supported (#) | Not supported | Supported (#) |
| Null values | Not natively supported | null keyword | null / ~ supported |
| Multiline strings | Triple-quoted strings | Escape \n manually | Literal/folded blocks |
| Date/time types | Native (RFC 3339) | String only | String only |
| Array of objects | [[table]] syntax | Array of {} objects | List of mappings |
| Spec version | TOML v1.0 (2021) | RFC 8259 | YAML 1.2 (2009) |
| Primary use case | Rust/Go/Python configs | APIs and data exchange | CI/CD and Kubernetes |
| Whitespace sensitive | No | No | Yes |
Frequently Asked Questions
Does TOML support null values from JSON?
TOML v1.0 has no native null type, which means JSON null values cannot be directly represented. During conversion, null keys are typically omitted from the output or converted to an empty string — check your converter's behavior and update your application logic to handle missing keys gracefully.
How does JSON to TOML convert nested objects?
Nested JSON objects become TOML tables, written as section headers in square brackets. For example, {"database": {"host": "localhost"}} becomes [database] on one line followed by host = "localhost". Deeply nested objects use dotted headers like [database.replica].
How are JSON arrays of objects converted to TOML?
Arrays of objects in JSON map to TOML's array of tables syntax, which uses double square brackets ([[tablename]]). Each element of the array becomes a new [[tablename]] block with its key-value pairs listed beneath it. This is specific to TOML and has no direct equivalent in JSON syntax.
Can I convert a JSON config file to TOML for use with Cargo or Hugo?
Yes — paste your JSON into the converter and the output will be valid TOML you can use with Rust's Cargo.toml, Hugo's config.toml, or Python's pyproject.toml. Make sure your JSON has no null values or keys that conflict with TOML reserved words, and verify the output against the relevant tool's schema.
What characters in JSON keys are invalid in TOML?
TOML bare keys only allow letters, digits, underscores, and dashes (A-Z, a-z, 0-9, -, _). JSON keys containing spaces, dots, or special characters must be quoted in TOML using double quotes (e.g., "my.key" = "value"). Dots in JSON keys are especially problematic because TOML interprets them as nested table separators.
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