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JSON Validator

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JSON Validator — Check & Validate JSON Syntax Online Free

What is JSON Validator?

Validate your JSON data and get detailed error messages with line numbers. Instantly find syntax errors in any JSON string.

JSON validation is a critical step in any development workflow that involves data interchange. Even a single misplaced comma, missing bracket, or unquoted key can cause an entire API request to fail or a configuration file to be rejected. Our JSON Validator parses your input using the browser's native JSON.parse engine and reports the exact error type and character position when validation fails. Unlike basic syntax checkers, this tool provides human-readable error messages that help you pinpoint problems quickly. For valid JSON, you get a clear confirmation message. The validator handles all JSON data types and structures including deeply nested objects, large arrays, Unicode characters, and escaped sequences. Because all validation happens in your browser, there is zero latency and your sensitive data never leaves your machine.

How to Use JSON Validator

  1. Paste or type your input into the editor on the left panel.
  2. Results update automatically while you type. You can also press Ctrl+Enter to force a refresh.
  3. View the result in the output panel on the right with full syntax highlighting.
  4. Use Copy or Download to export the result.
  5. Drag and drop .json or .txt files directly into the editor.
  6. Toggle Tree View for an interactive, collapsible view of the JSON structure.

Example

Input:

{"name": "Test", "items": [1, 2, 3], "valid": true}

Output:

✓ Valid JSON

Common Use Cases

  • Debugging API response errors before processing in your application
  • Validating JSON configuration files before deployment
  • Checking JSON payloads before sending POST/PUT requests
  • Verifying JSON data exported from databases or spreadsheets
  • Testing JSON output from code generators and templating systems

JSON Validator vs JSON Formatter

Purpose
Checks if JSON is syntactically correct
Reformats valid JSON with indentation
Output
Valid/Invalid status with error details
Reformatted JSON string
Modifies Input
No — read-only check
Yes — reformats whitespace
Error Reporting
Detailed error messages with position
Only shows parsing errors
Best For
Debugging broken JSON
Making valid JSON readable

Common Errors

  • Trailing comma after the last element — remove the comma before the closing bracket
  • Single quotes instead of double quotes — JSON strictly requires double quotes for strings and keys
  • Missing closing brackets — every { must have a matching } and every [ must have a matching ]
  • Undefined or NaN values — these are not valid JSON; use null instead
  • Unescaped special characters in strings — backslashes, newlines, and tabs must be escaped

Why Use Our JSON Validator?

  • 100% client-side — your data never leaves your browser. No server processing, no data collection.
  • No sign-up required — start using the tool instantly with no registration or installation.
  • Keyboard shortcuts — press Ctrl+Enter to run, ? for shortcuts list, Ctrl+B to toggle sidebar.
  • Persistent state — your input is automatically saved across sessions using local storage.
  • IDE-style interface — Monaco Editor (the engine behind VS Code) with syntax highlighting and error detection.
  • Multi-format conversion — convert between JSON, XML, CSV, and YAML without switching tools.

Frequently Asked Questions

What is JSON Validator?

JSON Validator is a free online tool that checks whether your JSON string is syntactically correct. It highlights exact error positions with detailed messages to help you fix issues quickly.

What types of errors can it detect?

It detects all JSON syntax errors including missing brackets, trailing commas, unquoted keys, invalid escape sequences, duplicate keys, and improperly nested structures.

Does JSON Validator modify my data?

No. The validator is read-only — it only checks your JSON for errors and never changes your input data. If you want to reformat your JSON, use the JSON Formatter.

What is the difference between JSON Validator and JSON Lint?

JSON Lint is another name for JSON validation. Our JSON Validator performs the same function as JSONLint — it parses your JSON and reports syntax errors. Both terms refer to checking JSON for correctness.

Can I validate very large JSON files?

Yes. Since validation runs in your browser, it can handle large JSON files limited only by your browser's memory. For files over 10MB, processing may take a few seconds.

Try JSON Validator Now

Paste your data into the editor above for instant processing. Use Ctrl+Enter anytime to re-run quickly.

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