JSON Validator

Validate JSON syntax and structure instantly. Identify errors with line numbers and detailed explanations to debug your JSON data quickly.

100% client-side No signup Free forever
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How to Use JSON Validator

  1. Paste or type your JSON data
  2. Click "Validate JSON" to check for errors
  3. Use "Format / Beautify" to pretty-print the JSON
  4. Use "Minify" to compress the JSON
  5. View the tree structure for easy navigation
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Features

  • Real-time JSON validation
  • Syntax error location
  • Format and beautify
  • Minify/compress
  • Tree view visualization
  • Statistics (size, depth, keys)
  • Auto-validate on paste
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About JSON Validator

JSON (JavaScript Object Notation) has become the standard format for data exchange in modern applications, APIs, and configuration files. Even a single misplaced comma or missing bracket can break your entire application. Our JSON Validator provides instant, precise validation to catch these errors before they cause problems.

How JSON Validation Works

The validator parses your JSON according to the official RFC 8259 specification, checking for:

  • Syntax errors: Missing quotes, commas, colons, brackets, or braces
  • Invalid values: Unquoted strings, trailing commas, single quotes
  • Structural issues: Unclosed arrays or objects, mismatched brackets
  • Encoding problems: Invalid Unicode sequences or control characters

Features That Save Time

Precise error location: When validation fails, you get the exact line number and character position where the error occurred, plus a clear explanation of what's wrong and how to fix it.

Real-time validation: As you type or paste JSON, the validator immediately shows whether your data is valid, eliminating the compile-test-fix cycle.

Pretty formatting: Valid JSON is automatically formatted with proper indentation, making it easier to read and understand complex nested structures.

Common JSON Errors and Solutions

The most frequent JSON mistakes include: using single quotes instead of double quotes for strings, adding trailing commas after the last item in arrays or objects, forgetting to quote property names, and using JavaScript-style comments (which JSON doesn't support). Our validator catches all these issues with specific guidance on how to correct them.

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Frequently Asked Questions

What makes JSON valid or invalid?
Valid JSON requires: double-quoted strings (not single), no trailing commas, no comments, properly nested brackets/braces, valid value types (string, number, boolean, null, object, array), and proper escaping. Our validator highlights exactly where errors occur.
Why is my JSON invalid? Common errors
Common errors: trailing commas ([1,2,3,] is invalid), single quotes ('key' must be "key"), unquoted keys ({name:"value"} must be {"name":"value"}), undefined/NaN values, and improper escaping of quotes or backslashes. We show specific error messages.
What is JSON Schema validation?
JSON Schema defines the expected structure of JSON data - required fields, data types, allowed values, patterns. Beyond syntax validation, schema validation ensures your JSON matches expected format. Useful for API contracts and data validation.
Can I validate JSON from a URL?
Yes! Enter a URL and we'll fetch and validate the JSON response. Useful for testing APIs directly. We show both syntax validation and can optionally validate against a schema. Note: CORS may prevent fetching from some URLs.
How do I fix malformed JSON?
Our repair feature attempts to fix common issues automatically: adding missing quotes, removing trailing commas, converting single quotes. For severely malformed JSON, we highlight problems and suggest fixes. Some data may require manual cleanup.
What is the difference between JSON and JSON5?
JSON5 extends JSON with: comments, unquoted keys, trailing commas, single-quoted strings, and multi-line strings. It's more human-friendly for configuration files. Standard JSON parsers won't accept JSON5 - convert to JSON for API use.