TOML to JSON Converter

Example: a Cargo.toml in TOML and JSON

[package]
name = "hello"
version = "0.3.1"

[[bin]]
name = "hello"
path = "src/main.rs"

[[bin]]
name = "hello-admin"
path = "src/admin.rs"

{
  "package": {
    "name": "hello",
    "version": "0.3.1"
  },
  "bin": [
    {
      "name": "hello",
      "path": "src/main.rs"
    },
    {
      "name": "hello-admin",
      "path": "src/admin.rs"
    }
  ]
}

How TOML types map to JSON

Every TOML value has a JSON counterpart, so the structure carries over in full. What changes is detail: JSON has one number type and no date type, so those values are written in the closest JSON form.

How are TOML arrays of tables converted to JSON?

Each [[name]] header starts a new object, and all objects with the same name are collected into one JSON array called name. Keys under a header belong to the most recent object, so a file with three [[bin]] blocks gives an array of three objects.

Why does 1.0 become 1 in JSON?

JSON has a single number type, so 1.0 and 1 are the same value once converted. The number is unchanged; only the TOML hint that it was a float is lost. If the difference matters, keep the TOML file as the source of truth.

How TOML dates and times appear in JSON

TOML has four date and time types. JSON has none, so each becomes an ISO 8601 string.

Does the converter keep the time zone offset?

Yes. An offset such as -08:00 is written exactly as it appears, never shifted to UTC. Fractions of a second are kept to the millisecond, so 00:32:00.999999 becomes00:32:00.999.

Fixing TOML errors

When the TOML is invalid, the converter names the problem, gives its line and column, marks the line in the editor and shows the broken lines underneath. The most common causes are:

• The same key or table twice. TOML does not allow a value to be redefined.
• Missing quotes. Text values need "double" or 'single' quotes.
• Spaces in bare keys. Write "my key" = 1, not my key = 1.
• An unclosed array or string, often a missing ] or " at the end of a line.

[server]
port = 8080

[server]
host = "0.0.0.0"

Invalid TOML document: trying to redefine an already defined table or value
Line 4, column 2

What does "trying to redefine an already defined table" mean?

A table header or key appears a second time. In the example above, [server] is opened twice. Move host under the first [server] and delete the second header.

Which TOML version does the converter support?

TOML 1.1.0, released in December 2025, and every file written for TOML 1.0. Version 1.1 adds inline tables that span several lines, trailing commas in inline tables, times without seconds such as07:32, and the \x and \e string escapes.

Where you convert TOML to JSON

Converting TOML to JSON usually means feeding a config file to a tool that only reads JSON:

• Cargo.tomlRead Rust package data in JavaScript tooling
• pyproject.tomlPass Python project settings to JSON-only CI steps
• hugo.tomlMove a Hugo site config to JSON
• wrangler.tomlMigrate Cloudflare Workers config to wrangler.jsonc
• netlify.tomlInspect build and redirect rules as data

TOML vs JSON

What is lost when converting TOML to JSON?

Comments, the difference between integers and floats, and the date types, which become strings. The data itself is kept in full. Values JSON cannot hold, inf and nan, are listed as warnings so nothing changes silently.

How do I convert JSON back to TOML?

Use the JSON to TOML converter. The Round-trip button above opens your JSON there in one click.

Is your TOML private?

Is my TOML file uploaded anywhere?

No. Opening a file reads it on your device. You can check this in your browser's network panel: converting makes no requests.