JSON YAML TOML Converter

What Is the JSON YAML TOML Converter?

The JSON YAML TOML Converter is a small online utility that changes structured data from one format to another. It converts in all six directions: JSON to YAML, JSON to TOML, YAML to JSON, YAML to TOML, TOML to JSON and TOML to YAML. You paste the data you already have, choose the format you want, and get back valid, consistently indented text ready to paste into a config file, a repository or a pipeline step.

The converter parses your input with a strict parser instead of doing risky text replacement, so nested objects, arrays, numbers, booleans and strings survive the trip with their types intact. If you are not sure what format your input is in, leave the source dropdown on Auto Detect and the tool reports what it recognised in a green badge next to the controls.

Why You Would Use It

Configuration lives in many dialects. Docker Compose and many CI systems want YAML, Rust and various build tools want TOML, and almost every API speaks JSON. Moving a value between those worlds by hand is slow and error prone: quote one string wrong, drop one comma, or mistype an indent and the file stops parsing. This tool does the whole rewrite for you in a single click.

It is aimed at developers converting a config file, DevOps engineers adapting a pipeline definition, QA engineers turning an API response into a fixture, students learning what the same data looks like in three syntaxes, and anyone who received a file in the wrong format. It also works as a formatter: converting a format to itself rewrites it with clean, consistent indentation and quoting.

How This Tool Works

The page has a header bar with a source dropdown (Auto Detect, JSON, YAML, TOML), a swap button, a target dropdown (JSON, YAML, TOML) and a Convert button. Below sit two editors. The left one is the Input, where you paste data; the right one is the Output, which is read only and shows the result. Language badges on both editors reflect your selection and update as soon as you change a dropdown.

When you press Convert, the tool checks for an empty input, then sends the text to the converter endpoint over HTTPS together with your chosen source and target. On the server, Auto Detect tries the input as JSON first, then as TOML, then as YAML, and takes the first format that parses into an object or array. The detected format is returned to the page and shown as a badge. Next the data is parsed with the strict parser for that format and serialised into the target format: JSON with pretty printing and unescaped slashes and unicode, YAML with two space indentation, or TOML with proper tables, nested tables and arrays of tables.

If anything fails, a red alert bar under the header explains the reason in plain language, for example Invalid JSON input, JSON input must be an object or array, YAML input must be a mapping or sequence, or Could not detect the input format. The output box is left empty so you never copy a half converted result. On success the output is filled and you press Copy to take it, or Swap to push it back into the input box for a second conversion.

Key Features

• All six conversion directions between JSON, YAML and TOML
• Automatic input detection with a visible detected-format badge
• Strict server-side parsing with clear, specific error messages
• Consistent output: pretty JSON, two space YAML, structured TOML tables
• Nested objects, arrays, arrays of tables, numbers, booleans and strings preserved
• Sample, Paste, Swap, Copy and Clear controls on both sides
• Language badges that follow your dropdown selection
• Convert a format to itself to reformat and reindent it

How to Use the Tool

1. Set the source dropdown. Leave it on Auto Detect if you do not know the format, or pick JSON, YAML or TOML explicitly.
2. Set the target dropdown to the format you need, then click Swap if you realise the two are the wrong way round (swap also exchanges the two editors).
3. Paste your data into the Input editor, or click Sample to load a ready-made example in the source format, or Paste to read your clipboard.
4. Click Convert. Watch the green badge for the detected format, or the red alert if the parser rejected the input.
5. Copy the result with Copy, or press Clear to empty a box. Use Swap to send the output back into the input when you need a chain such as TOML to JSON and then JSON to YAML.

Limits and Rules

Each conversion accepts up to 200,000 characters of input; anything larger is rejected by validation to keep responses fast. The conversion endpoint is rate limited to 30 requests per minute per client, so repeated clicking in a tight loop will return a throttling response and you should wait a moment before retrying.

The input must be a real document, not a fragment. JSON has to decode to an object or an array, so a bare string, number or boolean is refused with a clear message. YAML has to be a mapping or a sequence, so a plain scalar such as a single word is refused as well. TOML has to be a table. When Auto Detect cannot match any of the three parsers, it reports that and lists the supported formats.

Your data is sent to the server for conversion because all three parsers run there. The converter does not save your payload, and this endpoint runs without the request-tracking middleware, so nothing about your call is written to the database beyond the rate-limit counters. Do not paste secrets you are not allowed to send over the network, and remember that this tool converts structure, not semantics; it cannot repair a broken business rule inside your config.

When to Use It and When Not to

Use it when you inherited a config in the wrong dialect, when a deployment expects YAML but your editor exports JSON, when you want a TOML file rewritten with clean tables, or when you need a quick readable dump of an API response to share with a colleague.

Do not use it for very large exports beyond the character limit, for streaming or binary data, or as a schema validator; it converts data but does not check it against a schema. It also will not merge two files, reorder keys into a custom order, or comments: YAML comments and TOML comments are not carried into JSON, because JSON has nowhere to put them.