Online TOML to JSON Converter

What are TOML and JSON? When do you need to convert them?

If a software project's configuration file is written in TOML format (like config.toml), but the deployment system only recognizes JSON, you'll need to convert TOML to JSON. TOML (Tom's Obvious, Minimal Language) is a lightweight format specifically designed for configuration files, commonly found in Rust's Cargo.toml and Python's pyproject.toml. JSON (JavaScript Object Notation) is a data-interchange format supported by almost all programming languages and APIs. In our online converter, simply paste your TOML text into the left input box, click the "Convert" button, and the JSON output will appear on the right.

Typical Use Cases

• Deployment Configuration Migration: You wrote your development configuration in TOML locally, but the server only accepts environment variable files in JSON format. Use this tool to convert it once and copy the result to the server.
• Data Import and Export: A third-party API or database only supports JSON configurations, but you only have a TOML file. Convert it to JSON using the tool and submit it directly.
• Team Collaboration and Demos: When sharing configuration examples with colleagues unfamiliar with TOML, converting it to JSON helps more people intuitively understand the structure.

Complete Conversion Examples

Primary Example: A standard TOML configuration:

[server]
host = "127.0.0.1"
port = 8080

[database]
name = "testdb"
user = "admin"
password = "secret"

[features]
enable_ssl = true
allow_guests = false

Paste the above content into the "Input TOML" box of the tool, click "Convert", and the right side will display:

{
  "server": {
    "host": "127.0.0.1",
    "port": 8080
  },
  "database": {
    "name": "testdb",
    "user": "admin",
    "password": "secret"
  },
  "features": {
    "enable_ssl": true,
    "allow_guests": false
  }
}

Comparison Example: TOML containing arrays and datetimes:

title = "Example"
numbers = [1, 2, 3]
created = 2023-08-15T10:00:00Z

In the converted JSON, the datetime becomes a string:

{
  "title": "Example",
  "numbers": [1, 2, 3],
  "created": "2023-08-15T10:00:00Z"
}

Note that TOML arrays are preserved as-is, but datetimes are converted to ISO 8601 strings (since JSON does not have a native datetime type).

How to Interpret the Results

The successfully converted JSON can be copied and used directly. You should pay attention to a few differences:

• Keys remain unchanged, but dot-separated keys in TOML (e.g., a.b.c) will become nested JSON objects.
• Array of Tables (e.g., [[items]]) become arrays of objects in JSON, maintaining the same order as they appeared in the original TOML.
• Comments are lost: TOML's # comments do not exist in JSON and will be entirely discarded after conversion.

If the input TOML has syntax errors (such as duplicate keys or incorrect indentation), the tool will display an error message and will not output JSON.

Common Mistakes and Pitfalls

1. Forgetting to escape special characters: Double quotes inside TOML strings must be escaped with a backslash, otherwise parsing will fail. For example, say = "He asked: "Hello"" should be written as say = "He asked: "Hello"".
2. Confusing integers and floats: In TOML, 5 is an integer and 5.0 is a float; JSON will distinguish them accordingly and they cannot be mixed.
3. Relying on comments for explanations: If you use comments in the configuration file to explain field meanings, they will be lost after conversion, which can lead to misunderstandings. It is recommended to back up the original file before converting.
4. Array of tables merge order: If the same array of tables appears in two different places (e.g., [[items]] repeated at the beginning and end of the file), the TOML specification will merge them, causing the JSON array order to differ from expectations.
5. Non-standard date formats: TOML requires strict date formats (e.g., 2023-08-15T10:00:00Z). If written as 08/15/2023, it will be treated as a regular string.

Frequently Asked Questions (FAQ)

1. Can my TOML containing Chinese characters be converted normally? Yes. Both TOML and JSON support UTF-8 encoding, so Chinese characters (and other Unicode characters) will be preserved as-is.
2. Is the converted JSON completely equivalent to the original TOML? Not entirely. JSON lacks comments, date types become strings, and implicit table structures are not supported. The core data is consistent, but metadata is lost.
3. Does the tool support converting multiple TOML files at once? Currently, it only supports pasting a single block of text. If you need batch processing, we recommend using command-line tools (like toml2json).
4. Why is my TOML reporting a syntax error? Check if you are using spaces for indentation (do not use Tabs), if there are duplicate keys, and if strings are properly escaped. You can also use an online TOML validator to check it first.
5. Can I get a minified version (spaces removed) of the converted JSON? The default output is a pretty-printed format with indentation. If you need a minified version, you can copy the result into any JSON minifier tool.
6. Is it safe to convert if the TOML contains sensitive information (like passwords)? The tool runs entirely in your browser and does not upload your pasted content to any server. However, for absolute security, it is recommended to use it in an offline environment.

Notes and Limitations

• This tool strictly follows the TOML v1.0.0 specification but does not support certain edge features (such as trailing backslash line continuations or extra spaces inside inline tables). It will prompt an error when encountering unsupported syntax.
• Numeric precision is limited by JavaScript's Number type; integer values exceeding 2^53 may lose precision.
• The conversion results are for reference or temporary use; for critical configurations involving production environments, it is recommended to manually verify the converted JSON.
• If the tool fails to convert properly, try simplifying the TOML content and converting it in steps.

Now you can try your own TOML file in the converter above.