JSON Formatter and Validator

To format JSON, paste it into the Raw JSON Input box or select a .json file, then select Pretty Print. The formatter parses the text with your browser's JSON parser and re-indents it with 2 spaces by default, coloring keys, strings and numbers. If the JSON is invalid, it shows the line and column where parsing failed.

How to format JSON online

1. Add your JSON. Paste it into Raw JSON Input, drop a .json file on the upload box, or choose Select JSON File. Load Sample fills in a small test object if you just want to try it.
2. Choose the layout. Set Indentation to 2 spaces, 4 spaces or Tab. Set Object Keys to Sort keys A → Z if you want keys in alphabetical order at every level.
3. Format or minify. Select Pretty Print (Ctrl+Enter) for readable output or Minify JSON for one line. Validate only checks the syntax.
4. Use the result. Select Copy Output, or Download JSON to save a .json file named after the file you loaded. Output → Input moves the result back for another pass.

What does a JSON formatter do?

A JSON formatter (also called a JSON beautifier) parses your text into data and writes it back out with consistent indentation and one value per line. Nothing about the data changes: only the whitespace between tokens does. In JavaScript the basic job is one line, JSON.stringify(JSON.parse(text), null, 2). This page checks your text with JSON.parse but rebuilds the output from the text you pasted, so every number keeps its exact digits, and it adds syntax coloring, line numbers and a search box.

Here is a 55-character minified object:

{"user":{"id":7,"tags":["admin","beta"]},"active":true}

After Pretty Print with 2-space indentation it becomes:

{
  "user": {
    "id": 7,
    "tags": [
      "admin",
      "beta"
    ]
  },
  "active": true
}

The JSON Structure Tree under the editors shows the same data as collapsible objects and arrays, with counts such as Array(2). Use Expand All to open every level of a deeply nested API response at once.

How the JSON validator finds errors

The validator uses the browser's strict parser, which follows the JSON standard (RFC 8259). With Live Validation set to On while typing, it re-checks the input a fraction of a second after you stop typing. Smart debounce waits a little longer, which helps with large files, and Manual only waits for you to select Validate. When parsing fails, the status changes to Invalid JSON, the error badge shows the line and column, and that line number is highlighted in the gutter.

Most errors come from writing JavaScript object syntax instead of JSON:

The exact error text depends on your browser. Chrome usually reports "Unexpected token", while Firefox says "JSON.parse: expected double-quoted property name" or similar. The tool doesn't repair invalid JSON for you; it tells you where to look.

JSON pretty print vs minify: when to use each

Pretty print JSON when people will read it: config files, API responses you're debugging, fixtures in a code review. Indented JSON also produces cleaner line-by-line diffs. Minify JSON when a machine is the reader, such as a request body or a value stored in a database column. In the example above, the minified version is 55 characters and the 2-space version is 98, so whitespace almost doubled the size.

Two settings change the output beyond whitespace. Sorting keys makes two objects with the same content print identically, which helps before you compare two JSON files. Setting Unicode Output to ASCII escaped rewrites characters such as é as \u00e9, for systems that only accept plain ASCII.

What the formatter keeps and what it can't

• Key order stays as written unless you turn on sorting.
• Numbers keep their exact digits. JavaScript stores numbers as 64-bit floats, so JSON.stringify alone would turn 12345678901234567890 into 12345678901234567000 and 1.0 into 1. This formatter copies every number as written, in the output and in the tree.
• Duplicate keys collapse to the last one. {"a":1,"a":2} formats as {"a": 2}.
• JSON5 and JSONC (JSON with comments, like VS Code settings) are rejected because they aren't standard JSON.

Everything runs in your browser tab, so private payloads and tokens are never uploaded. If a value inside your JSON is a token, the JWT decoder will show its claims. To turn the data into a config file, use the JSON to YAML converter.

Frequently asked questions

Updated 11 October 2026Reviewed by the ToolzyLab teamHow we test our tools