DataFormattools
JSON · Validator

JSON Validator & Syntax Checker

Validate JSON syntax online with instant line and column error reporting. Check JSON validity, lint syntax, and detect malformed errors in your browser.

Syntax & Structure Validator
Paste or type data below to validate syntax and structure in real time.
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100% In-Browser Privacy: All conversions, formatting, and validations run purely on your machine using client-side JavaScript. Your data, code snippets, and environment variables are never transmitted to any server or recorded in logs.
Specifications

How JSON Validator Works

  • Executes strict JSON grammar parsing according to RFC 8259 and ECMA-404 specifications.
  • Calculates real-time structural metrics including total keys, object nesting depth, and byte size.
  • Pinpoints exact line numbers, column offsets, and error tokens for immediate correction.
Demonstration

Example Input & Output

Validates JSON syntax against RFC 8259 specifications, confirming quote pairing, bracket closure, and literal type correctness.

JSON Source Code
{
  "project": "DataFormatTools",
  "version": "1.0.0",
  "isValid": true,
  "supportedFormats": [
    "JSON",
    "YAML",
    "XML",
    "CSV",
    "ENV"
  ]
}
Expected Output
✓ Valid JSON (RFC 8259 Compliant)
- Total Keys: 4
- Max Depth: 2
- Document Size: 138 bytes
Applications

Common Use Cases

Configuration File Linting

Ensure critical configuration files like package.json, tsconfig.json, or workflow manifests are 100% syntactically valid before committing.

API Request Validation

Verify outgoing request bodies and webhook payloads before triggering cURL or Postman calls.

Guidelines

Key Specifications & Gotchas

Missing Quotes Around Keys

All object property keys must be wrapped in double quotes.

Unescaped Control Characters

Newlines and tabs inside string literals must be escaped as \n or \t.

Invalid Numeric Formats

Leading zeros (e.g. 0123) and hex notation (0xFF) are invalid in JSON numbers.

Questions

Frequently Asked Questions

How do I validate a JSON file online?

Paste your JSON content into the editor; the validator instantly checks syntax and reports any invalid tokens or syntax errors.

What causes JSON syntax errors?

Common causes include single quotes instead of double quotes, trailing commas after the last item, missing colons, and unclosed brackets.

What is the difference between JSON validation and schema validation?

Syntax validation checks if the document obeys RFC 8259 grammar rules, whereas schema validation verifies whether data matches expected fields and types.

Is my validated data stored or logged?

Never. Validation runs purely on your client device in memory.

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