{}JSON-Validator.net

JSON Validator Online — Instant Syntax Check

Paste your JSON and instantly find out if it's valid. Error messages point to the exact line and character — no guessing.

JSON Input
Result
🔍
Awaiting input
Paste JSON to validate
Common mistakes
{'key': 'val'}→ Double quotes only
{"a": 1,}→ No trailing commas
{key: "val"}→ Keys must be quoted
// comment→ No comments in JSON
⚡
Real-time validation
Results appear as you type — zero delay, zero button clicks needed.
🎯
Precise error location
Error messages include the exact line number and character position.
🔒
Fully private
All processing happens in your browser. Your JSON never touches a server.
📋
RFC 8259 compliant
Validates against the official JSON specification, not a lenient superset.

Most Common JSON Errors

90% of invalid JSON comes down to four mistakes:

Single quotes
Invalid
{'name': 'Alice'}
Valid
{"name": "Alice"}
Trailing comma
Invalid
{"a": 1, "b": 2,}
Valid
{"a": 1, "b": 2}
Unquoted keys
Invalid
{name: "Alice"}
Valid
{"name": "Alice"}
Comments
Invalid
{"key": "val" // note}
Valid
{"key": "val"}

Frequently Asked Questions

What does JSON validation check?+

It checks that your JSON strictly conforms to RFC 8259: properly matched braces and brackets, double-quoted keys, valid value types (string, number, boolean, null, array, object), no trailing commas, and no comments.

Why does my JSON with single quotes fail?+

Single quotes are not valid JSON. The JSON standard requires all strings — including object keys — to be wrapped in double quotes. Replace all single quotes with double quotes.

Why doesn't JSON allow trailing commas?+

The JSON specification (RFC 8259) explicitly disallows trailing commas. Remove the comma after the last item in any object or array.

Can JSON contain comments?+

No. Comments (// or /* */) are not part of the JSON specification. Remove all comments before validating or parsing JSON.

Is my JSON data safe?+

Yes. All validation runs locally in your browser using JavaScript's built-in JSON.parse(). Your data is never sent to any server.

Does this work on large JSON files?+

Yes. Since validation runs in your browser, there are no server-imposed file size limits. Very large files (100MB+) depend on your browser's available memory.

Want more guides? Browse all JSON guides →