Guides · 2026-04-04

What Is JSON, and How Do You Format It?

A beginner-friendly explanation of JSON, why it's everywhere, and how to format, validate, and fix messy JSON for free.

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JSON (JavaScript Object Notation) is the language apps use to swap data. If you've ever peeked at an API response, you've seen it. Here's what it is and how to make messy JSON readable.

The structure in 30 seconds

JSON stores data as key/value pairs inside curly braces, and lists inside square brackets:

{ "name": "Ada", "age": 36, "skills": ["math", "code"] }

• Keys are always in double quotes.
• Values can be text, numbers, true/false, null, objects, or arrays.
• Commas separate items; no trailing comma is allowed.

Why formatting matters

Minified JSON arrives as one long line — fine for machines, painful for humans. Formatting (or "pretty-printing") adds indentation and line breaks so you can read the structure. Validating catches the typos that break it, like a missing comma or an unclosed brace.

Format and validate for free

1. Paste your JSON into the free JSON Formatter.
2. It instantly indents valid JSON and points out errors in broken JSON.
3. Copy the clean result — or minify it again to save space.

Common errors it catches

• Single quotes instead of double quotes.
• A trailing comma after the last item.
• Missing closing } or ].

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