TMToolMetro

JSON Formatter

Format, minify, and validate JSON so structured data is easier to read and copy.

Developer Toolsavailable

Formatted JSON will appear here.

Runs locally in your browser.

About JSON Formatter

Use the JSON Formatter to turn compact JSON into readable, indented output or shrink formatted JSON into a single minified line. It is useful for checking API responses, config snippets, test data, logs, and copied structured data before you paste it into code, documentation, or another tool.

How to use

  1. Paste valid JSON into the input box.
  2. Click Format JSON to create readable 2-space indentation.
  3. Click Minify JSON when you need compact output without extra spaces or line breaks.
  4. Review any validation message if the JSON cannot be parsed.
  5. Copy the output when it is ready, or clear the tool to start again.

Worked example

API response cleanup

Sample input

{"user":{"id":42,"name":"Ava"},"roles":["editor","admin"],"active":true}

Formatted output

  • {
  • "user": {
  • "id": 42,
  • "name": "Ava"
  • },
  • "roles": [
  • "editor",
  • "admin"
  • ],
  • "active": true
  • }

Features

  • Formats valid JSON with readable 2-space indentation.
  • Minifies valid JSON into compact output.
  • Shows a clear validation message for empty or invalid input.
  • Supports objects, arrays, strings, numbers, booleans, and null values.
  • Keeps input and output side by side for quick comparison.
  • Runs in the browser without requiring an account.

How it works

  • The formatter trims the input and checks that something has been entered before parsing.
  • JSON is parsed with the browser's built-in JSON parser, so the tool follows strict JSON syntax.
  • Formatted output is created by serializing the parsed value with 2-space indentation.
  • Minified output is created from the same parsed value without extra indentation.
  • If parsing fails, the tool leaves the output empty and shows a practical error message.
  • Because the parsed value is serialized again, spacing and formatting are normalized in the result.

Common use cases

  • Making compact API responses easier to scan.
  • Checking JSON before adding it to documentation, examples, or support notes.
  • Cleaning config snippets and sample payloads before sharing them with a team.
  • Minifying JSON for a request body, fixture, or environment value.
  • Finding syntax problems such as trailing commas, missing quotes, or unmatched brackets.
  • Reformatting copied JSON from logs, browser tools, or debugging output.

Frequently asked questions

What does the JSON Formatter do?

It formats valid JSON with readable indentation, minifies JSON into compact output, and shows a validation message when the input cannot be parsed.

Does the JSON Formatter validate JSON?

Yes. The tool parses the input as strict JSON before formatting or minifying it. If parsing fails, it shows an error instead of producing output.

What indentation does formatted JSON use?

Formatted output uses 2-space indentation, which keeps nested objects and arrays readable without making the result too wide.

Can it minify JSON?

Yes. Use Minify JSON to remove unnecessary whitespace and line breaks from valid JSON.

Why does JSON with a trailing comma fail?

Trailing commas are not valid in strict JSON. Remove the comma after the final item in an object or array, then run the formatter again.

Do object keys need quotation marks?

Yes. Strict JSON requires object keys to be wrapped in double quotes, such as "name" rather than name.

Can I format a JSON array?

Yes. The formatter supports valid JSON arrays as well as objects, strings, numbers, booleans, and null values.

Does formatting JSON change the data?

The tool parses and serializes the JSON, so whitespace is normalized. The data values remain the same, but formatting and key spacing may change.

Is my JSON uploaded to ToolMetro?

No. The JSON Formatter runs in your browser and does not require server-side processing or an account.

What should I do if the formatter says the JSON is invalid?

Check for common syntax issues such as missing double quotes, trailing commas, unmatched braces, unmatched brackets, or text pasted before or after the JSON.