JSON Validator Guide — Validate & Check JSON Online
A complete guide to JSON validation. Learn how to check your JSON for syntax errors and fix common problems using our free JSON Validator.
What is JSON Validation?
JSON validation is the process of checking whether a JSON document conforms to the JSON specification (RFC 7159). A valid JSON document must follow strict syntax rules: keys must be double-quoted strings, values can be strings, numbers, booleans, null, arrays, or objects, and the structure must be properly nested with matching brackets and braces. Even a single syntax error can break an entire application that depends on JSON data.
How to Validate JSON Online
Using our JSON Validator is straightforward:
- Paste your JSON into the input area — the tool validates in real time as you type
- Check for errors — invalid JSON is highlighted with specific error messages showing the exact location of each problem
- Fix and re-validate — correct the errors and the tool automatically re-validates, giving you instant feedback
- Use the validated JSON — once valid, format it, copy it, or use it directly in your project
Common JSON Errors and How to Fix Them
Trailing commas
{ "name": "John", "age": 30, }JSON does not allow trailing commas after the last property or array element. Remove the comma after the final item.
Unquoted property names
{ name: "John" }JSON requires all property names to be wrapped in double quotes. JavaScript objects allow unquoted keys, but JSON does not.
Single quotes
{ 'name': 'John' }JSON only accepts double quotes for strings and property names. Single quotes are valid in JavaScript but not in JSON.
Mismatched brackets
{ "items": [1, 2, 3 }Objects use curly braces {} and arrays use square brackets []. They must be properly nested and matched.
Invalid number formats
{ "value": 01 }JSON does not allow leading zeros in numbers. Use 1 instead of 01, and use 0.5 instead of .5.
Valid JSON Examples
// ✅ Valid JSON object
{
"name": "Web Util Slyce",
"version": "1.0",
"features": ["json", "security", "seo"],
"active": true,
"count": 114
}// ✅ Valid JSON array
[
{ "id": 1, "name": "Alice" },
{ "id": 2, "name": "Bob" }
]JSON Validation Tips
Validate before formatting. Always validate JSON before formatting to catch errors early. Invalid JSON cannot be properly formatted.
Use a JSON viewer. After validation, use a JSON viewer to inspect the structure in a tree view for better understanding of nested data.
Check for empty objects. An empty pair of braces or brackets [] is valid JSON. Make sure your data structure is complete before using it.