JSON Formatter & Validator

JSON Editor

2 4 Tab

Input JSON

Output Ready

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Input Size

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Nesting Depth

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Total Keys

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Array Items

JSON Complexity —

Tip: Press Format to auto-indent your JSON. Use Minify to strip whitespace for production API payloads. All processing runs entirely in your browser — no data is ever sent to any server.

How It Works

Paste Your JSON

Paste raw, minified, or poorly-formatted JSON into the input box.

Choose an Action

Click Format to pretty-print, Minify to compress, or Validate to check for errors.

Copy or Use Output

The processed JSON appears on the right. Use Copy to grab it in one click.

JSON Format Rules (ECMA-404 / RFC 8259)

// A JSON value must be one of: string → "enclosed in double quotes" number → 42 | 3.14 | -7 | 1.2e10 boolean → true | false null → null object → { "key": value, … } ← keys MUST be strings array → [ value, value, … ] // Common mistakes this validator catches: ✗ Trailing commas → { "a": 1, } ✗ Single quotes → { 'key': "value" } ✗ JS comments → // not allowed in JSON ✗ Unquoted keys → { key: "value" }

JSON Data Type Reference

Type	Example	Notes	RFC 8259
String	`"Hello World"`	Must use double quotes; escape special chars with \	§7
Number	`42, -3.14, 1e5`	No octal/hex; NaN and Infinity are not valid	§6
Boolean	`true, false`	Lowercase only — True or FALSE will fail	§3
Null	`null`	Represents absence of a value	§3
Object	`{"k":"v"}`	Unordered key-value pairs; keys must be strings	§4
Array	`[1,"a",true]`	Ordered list; mixed types are allowed	§5

Frequently Asked Questions

JSON (JavaScript Object Notation) is a lightweight, text-based data-interchange format. Defined in ECMA-404 and RFC 8259, it is the most widely used format for REST API responses and configuration files.

Format (pretty-print) adds indentation and line breaks to make JSON human-readable. Minify removes all unnecessary whitespace to produce the smallest possible payload — ideal for production APIs where every byte counts.

Common reasons: trailing commas after the last key/element, single-quoted strings instead of double quotes, JavaScript-style comments (// or /* */), unquoted keys, or using undefined/NaN/Infinity — which are JavaScript values but not valid JSON.

Absolutely. This tool runs 100% in your browser. No data is transmitted, logged, or stored anywhere. You can safely use it with confidential API payloads and production secrets.

2 spaces is the most common convention (Node.js, most JS style guides). 4 spaces is preferred in Python (PEP 8). Tabs are favoured by some Go and C developers. All produce valid JSON — the choice depends on your team's style guide.

The JSON spec does not forbid duplicate keys, but behaviour is undefined — different parsers may keep the first, last, or all values. In practice, always use unique keys to guarantee consistent results across environments.

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Authority Sources & Standards

ECMA-404 — The JSON Data Interchange Syntax (2nd edition, 2017)
ecma-international.org → ECMA-404

RFC 8259 — The JavaScript Object Notation (JSON) Data Interchange Format
rfc-editor.org → RFC 8259

JSON.org — Introducing JSON (Douglas Crockford)
json.org

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