JSON Validator: Check Syntax and Find Errors Instantly

How to use the json validator

1. Paste or type your text into the JSON input field.
2. The json validator checks the syntax automatically as you type.
3. If valid, review the statistics including depth, keys, and size.
4. If invalid, read the error message and note the exact line and column.
5. Fix the issue in your source file and paste the corrected text back.

What makes JSON valid

The JSON specification (RFC 8259) defines a strict grammar. To validate json successfully, your text must follow these rules:

• Data is enclosed in curly braces {} for objects or square brackets [] for arrays.
• Object keys must be double-quoted strings. Single quotes are not allowed.
• Strings must use double quotes. Unquoted words are only valid for true, false, and null.
• Numbers cannot have leading zeros (except 0 itself) and cannot be NaN or Infinity.
• No trailing commas are permitted after the last item in an array or object.
• No comments of any kind (// or /* */) are allowed.

A common mistake when using a json validator is pasting JavaScript object notation instead of strict JSON. For example, {key: 'value'} is valid JavaScript but fails JSON validation because the key lacks double quotes and the string uses single quotes.

Understanding error messages

When you validate json that contains a syntax error, the parser stops at the first character it cannot process. The error message typically includes a description and a position. This tool converts that position into a human-readable line and column number.

Consider this broken input:

{"name": "test",}

The parser encounters the closing brace immediately after a comma, which violates the grammar. The reported position points directly to the }. Removing the trailing comma fixes the issue. Another frequent error is forgetting to escape internal quotes within a string, such as {"msg": "He said "hi""}, which should be written as {"msg": "He said \"hi\""}.

If you need to convert validated data into another format, tools like json to csv can help once your syntax is confirmed correct.

JSON Validator vs JSONLint

JSONLint was one of the first popular web-based tools to validate json, and its name became synonymous with the task. However, sending data to a remote server for linting raises privacy concerns when working with sensitive configuration files, API responses, or proprietary data structures.

This json validator performs the same syntax checking entirely in your browser. No network requests are made. It uses the native JSON.parse() method available in all modern browsers and Node.js environments, ensuring standard-compliant validation without external dependencies.

While dedicated linters might offer stylistic opinions (like enforcing two-space indentation), a validator focuses strictly on structural correctness. If you need to reformat valid data, use a json formatter after confirming it passes validation.

Common JSON mistakes reference

The table below lists frequent errors encountered when developers try to validate json, along with their corrections.

Keeping this list handy speeds up debugging when your json validator reports an unexpected token.

Working with parsed data

Once you validate json successfully, you often need to manipulate it programmatically. In JavaScript, JSON.parse() converts the text into an object, while JSON.stringify() does the reverse. If you are building workflows that require serializing objects back to text safely, the json stringify tool handles escaping and formatting options.

For comparing two validated payloads to spot differences in structure or values, a json diff utility highlights exactly what changed between versions. Validating first ensures that comparison tools do not fail on syntax errors before they even begin analyzing content.

Worked examples

Each result below was produced by the same code the tool runs, so you can check your own numbers against them.