Explore Tools

JSON Formatter & Validator

Beautify messy JSON, minify it for production, or find syntax errors with the exact line and column, all privately in your browser.

  • Exact error location
  • Works offline once loaded
  • Data never uploaded

How to use the JSON Formatter tool

  1. Paste or open your JSONPaste JSON from an API response, log file or config, or open a .json file from your computer.
  2. Choose formatting optionsPick 2 spaces, 4 spaces or tabs, and optionally sort object keys alphabetically.
  3. Format, minify or validateClick “Format / Beautify” for readable output, “Minify” for the smallest size, or “Validate only” to check syntax.
  4. Copy or downloadCopy the result to your clipboard or download it as a .json file.

Why developers use this JSON formatter

  • Pinpoint errorsInvalid JSON shows the line and column of the problem plus a hint for common mistakes like single quotes or trailing commas.
  • Beautify & minifySwitch between human-readable indentation and compact single-line output in one click.
  • Sort keysAlphabetical key order makes two JSON documents easy to compare in a diff tool.
  • Private by designParsing uses your browser’s built-in JSON engine. Tokens, customer data and API keys never leave your machine.
  • Large filesHandles multi-megabyte files quickly because nothing has to be uploaded.
  • Keyboard shortcutPress Ctrl + Enter (Cmd + Enter on Mac) inside the input to format instantly.

What is JSON?

JSON (JavaScript Object Notation) is a lightweight text format for structured data. It is the standard way web APIs send data, and it is used for configuration files, databases such as MongoDB, and data exchange between almost every programming language. A JSON document is built from objects ({ }), arrays ([ ]), strings, numbers, booleans (true/false) and null.

APIs usually return JSON minified on a single line to save bandwidth. That is efficient for computers but hard for people to read. A JSON formatter adds line breaks and indentation so you can see the structure at a glance.

Common JSON syntax errors

JSON is stricter than JavaScript. These are the mistakes our validator catches most often:

  • Single quotes. Strings and keys must use double quotes: {"name": "Ann"}, not {'name': 'Ann'}.
  • Trailing commas. A comma after the last item, as in [1, 2, 3,], is not allowed.
  • Unquoted keys. {name: "Ann"} is valid JavaScript but invalid JSON.
  • Comments. Standard JSON has no comments. Remove // and /* */ lines before parsing.
  • Special values. undefined, NaN and Infinity are not valid JSON values. Use null or a number instead.
  • Unescaped characters. Line breaks and double quotes inside a string must be escaped as \n and \".

Beautify or minify?

Use beautified JSON while developing, reviewing API responses or committing configuration files to version control, because readable files produce clearer diffs. Use minified JSON when sending data over the network or storing it in production, where every byte counts. Minifying removes only whitespace, so the data itself is unchanged.

Is it safe to paste API responses here?

Yes. Many online formatters send your data to a server for processing. This one does not: the formatting and validation run entirely inside your web browser using the same JSON engine your browser uses for every website. You can even disconnect from the internet after the page loads and the tool keeps working. Even so, it is good practice to remove passwords and live API keys before sharing JSON with anyone.

Frequently asked questions

Is this JSON formatter free?
Yes. It is free with no usage limits and no account required.
Is my JSON data sent to a server?
No. Everything happens locally in your browser, so confidential data such as tokens or customer records never leaves your device.
Why does my JSON show an error when it works in JavaScript?
JSON is a stricter subset of JavaScript object syntax. It requires double quotes around keys and strings and does not allow trailing commas, comments or values like undefined. The error message shows the exact line and column to fix.
What does “Sort keys A–Z” do?
It reorders the keys inside every object alphabetically, at all nesting levels. Arrays keep their original order because the order of array items is meaningful.
Is there a file size limit?
There is no fixed limit. Files of several megabytes format in about a second on a modern computer. Extremely large files are limited only by your browser’s memory.