Why does my JSON fail validation even though it looks correct?

The most common hidden issues are trailing commas after the last item in an array or object, single-quoted strings, unquoted property names, or JavaScript-specific values like undefined, NaN or Infinity. JSON is strictly defined by RFC 8259 and is more restrictive than JavaScript object literal syntax.

What is the 'Sort Keys' mode useful for?

Sorting keys recursively normalizes JSON objects so their content can be compared accurately with text diff tools, regardless of the order in which keys were inserted. This is particularly useful when comparing API responses between environments or validating that two objects are semantically identical.

Developer Utilities

JSON Formatter & Validator

The problem: Raw API responses and log files are often single-line minified JSON that is unreadable by humans, or conversely, bloated formatted JSON that wastes bandwidth.

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100% In-Browser Execution. Zero server uploads. Your data never leaves this tab — disconnect your internet and the tool keeps working.

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100% In-Browser Execution. Zero server uploads. Your data never leaves this tab — disconnect your internet and the tool keeps working.

Indent:

Input JSONObject{7 keys}

Output

17 lines·10 keys·288 B(+6%)

{
  "id": 42,
  "name": "Priya Sharma",
  "email": "priya@example.com",
  "role": "developer",
  "createdAt": "2024-01-15T09:30:00Z",
  "preferences": {
    "theme": "dark",
    "notifications": true,
    "language": "en"
  },
  "tags": [
    "react",
    "typescript",
    "nodejs"
  ]
}

JSON Formatter & Validator: the complete guide

A JSON formatter, validator and minifier transforms raw JSON data between human-readable and machine-optimized representations — an essential daily-use tool for web developers, API engineers, data analysts and DevOps engineers. Raw API responses are typically minified single-line JSON that is impossible to read. Development logs and configuration files need to be compact for storage but readable during debugging. This tool provides three transformation modes: Pretty Print (with configurable 2 or 4-space indentation), Minify (strip all whitespace), and Sort Keys (alphabetical, recursive).

JSON validation: why the error position matters

The most common JSON errors are: trailing commas after the last array element or object property (not allowed in JSON, only in JavaScript), unquoted keys (valid in JS object literals but not JSON), single-quoted strings (JSON requires double quotes), and undefined or NaN values (not valid JSON primitives). This formatter shows the exact error message from JSON.parse() with an estimated line number to help you navigate directly to the problem.

Key sorting for reproducible diffs

The Sort Keys mode recursively sorts all object keys alphabetically at every nesting level. This is invaluable for comparing two JSON objects from different sources, normalizing API responses for unit test fixtures, ensuring configuration files are deterministically ordered in version control (so Git diffs only show meaningful content changes, not key-ordering noise), and debugging payload differences between environments.

Step by step: how to use JSON Formatter

1
Paste your JSON in the left panel, or click a sample button (User or API) to load example data.
2
Select the output mode: Pretty Print, Minify, or Sort Keys.
3
For Pretty Print, choose 2-space or 4-space indentation.
4
The formatted output appears in the right panel instantly.
5
Review the stats bar: line count, key count, byte size, and size change percentage.
6
Click Copy JSON to copy the output to your clipboard.

Security & privacy

All JSON parsing and transformation runs in your browser using JavaScript's native JSON.parse() and JSON.stringify() functions. The JSON data you paste — which may include API keys, PII, database records or configuration secrets — never leaves your browser tab. No network requests are made during formatting. The tool is safe to use with production data.