JSON Validator
Validate JSON syntax instantly with detailed error messages and line numbers. Free online tool that runs 100% in your browser.
What does a JSON validator do?
A JSON validator checks whether a text string follows the correct JSON (JavaScript Object Notation) syntax. It identifies errors like missing commas, unmatched brackets, invalid quotes, and trailing commas, reporting them with precise line and column numbers.
How does JSON validation work?
The tool uses the browser's built-in JSON parser to attempt parsing your input. If parsing succeeds, the JSON is valid and the tool displays structure information. If it fails, the parser returns the exact position of the first syntax error.
What information is shown for valid JSON?
For valid JSON, the tool displays the root data type (object, array, string, number, boolean, or null), the nesting depth, and for objects the number of keys or for arrays the number of items.
What are common JSON syntax errors?
The most common errors include: missing or extra commas, using single quotes instead of double quotes, trailing commas after the last property, unquoted keys, comments (not allowed in standard JSON), and unmatched braces or brackets.
Does JSON support comments?
No, the official JSON specification (RFC 8259) does not support comments. If you need annotated JSON, consider using JSON5 or JSONC format, though these are not standard JSON.
What is the difference between JSON and a JavaScript object?
JSON is a text format for data exchange, while JavaScript objects are in-memory data structures. Key differences: JSON requires double quotes for all strings and keys, does not support functions or undefined values, and has stricter syntax rules.
Is my data safe and private?
Yes. All JSON validation happens entirely in your browser. Your data is never sent to any server or uploaded anywhere. It remains 100% on your device.
Can this tool handle large JSON files?
Yes. Since validation runs locally in your browser using native JSON parsing, it can handle large JSON files efficiently. Performance depends on your device's memory and processing power.
What data types does JSON support?
JSON supports six data types: strings, numbers, booleans (true/false), null, objects (key-value pairs), and arrays (ordered lists). Numbers include both integers and floating-point values.
How do I fix invalid JSON?
Read the error message carefully — it shows the exact line and column where the parser encountered the problem. Common fixes include: adding missing commas, replacing single quotes with double quotes, removing trailing commas, and ensuring all brackets are matched.
What is JSON lint?
JSON lint refers to a tool that checks JSON code for syntax errors and style issues, similar to how lint tools work for programming languages. This validator serves as a JSON lint checker.
Can I validate JSON from an API response?
Yes. Simply copy the JSON response from your API call and paste it into the validator. This is useful for debugging API responses during development.
How to Use JSON Validator
Check any JSON for syntax errors instantly, with exact line and position details. Everything is analyzed locally in your browser — invalid or private payloads never leave your machine.
- Paste your JSON into the input editor; validation runs automatically as you type.
- Read the result panel: valid input shows a success state, broken input shows a descriptive error.
- Use the reported line and position to jump straight to the offending character, such as a missing comma or bracket.
- Fix the highlighted issue and re-check until the validator reports your JSON as valid.
Trailing commas after the last item of an object or array are the most common JSON error — they are fine in JavaScript but invalid in strict JSON.
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