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JSON Validator

Validate JSON syntax instantly. Get detailed error messages with position information, structure analysis — keys, depth, arrays — all in the browser.

Input
Output
Ready — paste your input and click Format
Try a sample: Simple Object Nested JSON JSON Array
📊 Stats
—
Total Keys
—
Max Depth
—
Arrays
—
Size
⌨️ Shortcuts
Ctrl+EnterValidate JSON
Ctrl+Shift+CCopy output
Ctrl+LClear all
TabInsert indent in editor
💡 Tips
🔑
Keys must be strings wrapped in double quotes — {name:"x"} is invalid; {"name":"x"} is correct.
🚫
No trailing commas — a comma after the last array item or object property causes a parse error in JSON.
🔢
null not undefined — JSON supports null but not JavaScript's undefined.
💬
No comments — JSON does not support // or /* */ comments.
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JSON Validation Rules

JSON has strict syntax rules derived from JavaScript object notation. Keys must be double-quoted strings. Values must be one of: string, number, boolean (true/false), null, array, or object. No trailing commas, no comments, no undefined values, and no single quotes.

Common JSON Errors

  • Single-quoted strings — JSON requires double quotes for all strings
  • Trailing commas — no comma allowed after the last item in an array or object
  • undefined values — use null instead
  • Comments — JSON does not support any comment syntax

Frequently Asked Questions

The most subtle JSON errors are: (1) a trailing comma after the last property in an object or last element in an array, (2) a BOM (byte order mark) character at the start of the file (invisible in most editors), (3) using curly quotes (“”) copied from a word processor instead of straight quotes.
For minor issues like trailing commas or comments, try json5 or jsonc parsers. For larger issues, manually review the error position shown by this validator. The JSON Formatter tool will also show the error position when it fails to parse.
JSONP (JSON with Padding) wraps JSON in a function call like callback({...}) to bypass old browser cross-origin restrictions. It is not standard JSON and will fail JSON.parse(). Modern APIs use CORS instead of JSONP.
Done!

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What is JSON Validator?

JSON Validator is a free online utility designed to help developers, designers, and technical professionals work more efficiently. This tool runs entirely in your browser — no installation required, no data sent to any server.

How to Use JSON Validator

  1. Paste or type your input in the editor area above.
  2. Click the action button to process your content.
  3. Copy the output or download the result.

Key Features

  • 100% Free — No registration or payment required.
  • Client-side Processing — Your data never leaves your browser.
  • Instant Results — Get output in milliseconds.
  • No Installation — Works directly in your web browser.
  • Mobile Friendly — Works on phones, tablets, and desktops.

Who Uses JSON Validator?

This tool is widely used by web developers, software engineers, data analysts, students, and IT professionals who need a quick and reliable way to process data without setting up complex software environments.

Frequently Asked Questions

Is JSON Validator free to use?
Yes, JSON Validator is completely free. There are no hidden charges, no subscription fees, and no account required.
Is my data safe when using JSON Validator?
Absolutely. All processing happens locally in your browser. No data is uploaded to any server, making it completely private and secure.
Can I use JSON Validator on mobile devices?
Yes, JSON Validator is fully responsive and works on all modern browsers and devices including smartphones and tablets.
Do I need to install anything to use JSON Validator?
No installation is required. Simply open the page in your browser and start using it immediately.
How accurate is JSON Validator?
JSON Validator uses industry-standard algorithms to ensure accurate and reliable results every time.

About This JSON Validator

A single syntax error or misconfiguration can break an entire application or cause security vulnerabilities. This free online JSON Validator lets you instantly verify your JSON for errors, mismatches, and invalid syntax before deploying or using it in production.

How to use

  1. Paste or type your JSON input into the tool.
  2. Click Validate or the check button.
  3. Review any errors or warnings highlighted in the output.

Why validate online?

Use this tool regularly during development to maintain high-quality, error-free JSON and catch problems early in the workflow.

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Frequently Asked Questions

Is this JSON Validator free to use? +
Yes, completely free. No signup, no account, no payment required. Just paste your input and use it directly in your browser.
Does this tool store or send my data anywhere? +
No. Everything runs entirely in your browser using JavaScript. Your data never leaves your device or gets sent to any server.
What browsers does this tool support? +
It works in all modern browsers — Chrome, Firefox, Safari, Edge, and Opera — on both desktop and mobile.
Can I use this tool offline? +
Once the page is loaded, the tool runs locally in your browser without needing an active internet connection for most operations.
🔧
Custom Development

Need a Custom Version of This Tool?

This JSON Validator works for most use cases — but if you need batch processing, API access, private hosting on your own domain, or a completely bespoke tool built around your workflow, I can build it.

Request Custom Build → Typical turnaround: 3–7 days