What is JSON Validation?
JSON validation is the process of checking whether a text string conforms to the JSON (JavaScript Object Notation) specification defined in RFC 8259. A valid JSON document must follow strict syntax rules: strings must use double quotes, no trailing commas are allowed, keys must be quoted, and comments are not permitted.
Even a single misplaced character — a missing comma, an extra bracket, or a single quote instead of a double quote — can cause an entire JSON document to fail parsing in applications and APIs.
How to Use This Validator
- Paste your JSON text into the Input tab, or click Upload to load a file from your computer.
- Click Validate to check the syntax. Enable Live Validate for real-time checking as you type.
- If valid, you will see a summary with key counts, depth, and file size. If invalid, the exact error location (line and column) is highlighted.
- Click Auto Fix to automatically correct common issues like trailing commas, single quotes, unquoted keys, and comments.
Common JSON Syntax Errors
- Trailing commas — JSON does not allow a comma after the last item in an object or array:
{"a":1,} is invalid.
- Single quotes — All strings must use double quotes:
{'name':'value'} should be {"name":"value"}.
- Unquoted keys — Object keys must be strings in double quotes:
{name:"value"} is invalid.
- Comments — JSON does not support
// or /* */ comments. Use JSONC or JSON5 formats if you need comments.
- Missing brackets — Every
{ needs a matching }, and every [ needs a matching ].
Frequently Asked Questions
What does the Auto Fix feature do?
Auto Fix attempts to correct common JSON mistakes automatically. It removes trailing commas, converts single quotes to double quotes, adds quotes to unquoted keys, and strips JavaScript-style comments. After applying fixes, it re-validates the result.
Is JSON validation the same as JSON Schema validation?
No. This tool performs syntax validation — it checks if your text is valid JSON according to the JSON specification. JSON Schema validation is a separate process that checks whether valid JSON conforms to a specific structure or data model you define.
Why does my JSON work in JavaScript but fail validation?
JavaScript is more lenient than the JSON specification. JavaScript allows single quotes, unquoted keys, trailing commas, and comments — none of which are valid in strict JSON. Use our Auto Fix to convert JavaScript object notation into valid JSON.