What is a JSON Validator?

A JSON Validator checks whether your JSON data is syntactically correct according to the JSON specification (RFC 8259). It identifies errors like missing commas, unclosed brackets, invalid escape sequences, and trailing commas — all in real-time, right in your browser.

What errors can the JSON Validator detect?

Our validator detects missing or extra commas, unclosed brackets and braces, invalid string escapes, single quotes instead of double quotes, trailing commas, unquoted keys, duplicate keys, and other RFC 8259 syntax violations.

Can the validator fix my JSON automatically?

Yes. Our Smart Auto-Repair feature can automatically fix common JSON errors like trailing commas, single quotes, unquoted keys, and missing brackets with one click.

Is JSON validation done securely?

Yes. All validation happens entirely in your browser using JavaScript. Your JSON data is never uploaded or sent to any server, ensuring complete privacy and compliance with strict data-handling policies.

What is the difference between JSON validation and JSON Schema validation?

JSON validation only checks if data follows correct JSON syntax. JSON Schema validation goes further by checking the data conforms to a predefined structure with specific data types, required fields, and value constraints.

Can it validate large JSON files?

Yes. The validator is optimized to handle multi-megabyte JSON files smoothly. Because everything runs locally, file size is only limited by your device memory.

Does it work offline?

Once the page is loaded the validator works fully offline — perfect for working with sensitive payloads on locked-down networks.

JSON Validator - Check and Validate JSON Online

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Why Use Our JSON Validator?

Detailed Error Reports

Get precise error messages with line and column numbers pointing to exactly where the problem is in your JSON.

Auto-Fix Errors

Smart Auto-Repair fixes common errors like trailing commas, single quotes, and unquoted keys instantly.

Private & Secure

All validation runs locally in your browser. Your data never leaves your device.

Understanding JSON Validation

JSON (JavaScript Object Notation) is the most widely used data-interchange format on the web, but a single misplaced comma or quote can break an entire payload. A JSON validator gives you instant, line-accurate feedback so you can fix issues before they reach production.

Common JSON Syntax Errors

Trailing commas — JSON does not allow a comma after the last item.
Single quotes — JSON requires double quotes for keys and string values.
Unquoted keys — every object key must be wrapped in double quotes.
Unclosed brackets — every { needs a matching }, every [ needs a ].
Invalid escape sequences — only specific backslash escapes are allowed inside strings.

When To Use a JSON Validator

Use the validator while debugging API responses, editing config files, copying payloads from logs, or preparing data for ingestion pipelines. The earlier you catch a malformed payload, the cheaper the fix.

Free JSON Validator - Check JSON Syntax