Free JSON Formatter & Validator Online — Pretty Print JSON

Where you'll find JSON

• APIs: Every major web API returns JSON. Twitter, Google Maps, Stripe, GitHub — all of them. You call an endpoint, you get JSON.
• Configuration files: package.json (Node.js), composer.json (PHP), manifest.json (Chrome extensions), settings.json (VS Code).
• Databases: PostgreSQL, MongoDB, and others store JSON data directly.
• Data transfer: Sending data from a server to a browser. From one application to another.

What JSON looks like

JSON uses two structures:

Key-value pairs (objects):

Ordered lists (arrays):

You can nest them arbitrarily deep:

The problem with minified JSON

Try finding the second order total in that mess. It's buried.

The solution: pretty print JSON

Formatted JSON uses indentation (usually 2 or 4 spaces) and line breaks. Same data. Actually readable. Now you can find the second order total in seconds. Formatting saves minutes of squinting.

When developers use this

• Debugging API responses: Call an endpoint. Copy the response. Paste into JSON formatter. See the structure instantly.
• Validating config files: package.json with a missing comma breaks your build. Paste it here. The validator shows exactly where.
• Cleaning up data before import: Need to examine a large JSON dataset. Format it first. Then search, edit, or extract what you need.
• Sharing JSON with teammates: Send formatted JSON. Your coworker can read it without using their own formatter.

Missing comma

Error: "name": "John" "age": 30

Fix: Add comma after "John" → "name": "John", "age": 30

Why it happens: You forgot the separator between properties. JSON requires commas between key-value pairs in the same object.

Trailing comma

Error: {"name": "John", "age": 30,}

Fix: Remove the comma after 30 → {"name": "John", "age": 30}

Why it happens: Some languages allow trailing commas. JSON does not. The last property cannot have a comma after it.

Unquoted keys

Error: {name: "John"}

Fix: Add quotes around name → {"name": "John"}

Why it happens: JavaScript allows unquoted keys. JSON does not. Every key must be in double quotes.

Single quotes instead of double

Error: {'name': 'John'}

Fix: Replace single quotes with double → {"name": "John"}

Why it happens: JSON requires double quotes. Single quotes are not valid.

Mismatched brackets

Error: {"name": "John", "items": ["apple", "banana"]

Fix: Add missing } at the end → {"name": "John", "items": ["apple", "banana"]}

Why it happens: You opened two brackets { and [ but closed only one ]. The validator shows exactly which bracket is missing.

Missing colon

Error: {"name" "John"}

Fix: Add colon between key and value → {"name": "John"}