What is it
JSON Formatter is a free online tool that organizes, validates and minifies data in JSON format, the most used text format for exchanging information between systems, APIs and configuration files. If you've never heard of JSON, think of it as a standardized way of writing data (names, numbers, lists) in a way that both programs and people can read.
The tool takes raw JSON, often returned by an API in a single, compact and difficult-to-follow line, and returns the content indented, with spacing and line breaks that make it easier to read and review. If the pasted JSON has any syntax error, such as a missing comma, single quotes instead of double quotes or a missing brace, the tool points out the exact error message, returned by the parser itself, which helps to locate the problem quickly without having to search character by character.
When the JSON is valid, a panel shows statistics for the object: the total number of keys, the maximum nesting depth, and the estimated size in bytes or KB. This helps you quickly understand the size and complexity of an API response before working with it in code, including when the pasted JSON is an array rather than an object.
In addition to formatting and minifying, the tool has a TypeScript tab: when pasting a JSON, it automatically generates the corresponding TypeScript interface, ready to copy and paste into a code project. This saves you the trouble of writing typing manually every time a new endpoint returns a different data format.
How to use
- Paste the JSON into the field on the left of the tool.
- Click Format to indent the content, Minify to leave everything on one line, or TS Type to generate the TypeScript interface.
- Choose between 2 or 4 space indentation in the options menu when using formatted mode.
- Check the total keys, depth and size statistics displayed above the result, when the JSON is valid.
- If there is a syntax error, read the message returned by the parser to locate the exact point of the problem and correct it.
- Click Copy to take the result directly to your project, terminal or document.
Tips
- Use the minified version to reduce the size of a payload before sending, and the formatted version to review or present content.
- The most common errors in JSON are an extra comma at the end of a list, single quotes instead of double quotes and square brackets or braces without closing. The tool follows the strict JSON standard, so comments and leftover commas (common in JSON5 or JSONC) also generate syntax errors here.
- The TypeScript tab is useful for those who frequently consume APIs and need to keep the project's typing updated without typing everything manually.
- All processing runs within your browser, so production data and sensitive information do not travel through any external server.