How to use the JSON Validator
1. Paste your JSON data into the input box below.
2. Click Validate JSON to check if the JSON is valid.
3. If valid, you'll see a green success message with basic stats about the JSON structure.
4. If invalid, the exact error message is shown with the line and column number of the problem.
What is it?
JSON (JavaScript Object Notation) is a strict format — even a single misplaced comma, missing quote, or unescaped character makes the entire document invalid. This validator uses the browser's native JSON.parse() function to definitively determine if a JSON string is well-formed.
Common JSON errors include: trailing commas after the last element in an array or object (valid in JavaScript but not JSON), single-quoted strings (JSON requires double quotes), unescaped special characters in strings, and NaN or Infinity values (not valid JSON primitives).
This tool helps you quickly identify exactly where the parsing error occurs by reporting the line and column number, saving debugging time when working with large API responses or configuration files.
Example
{'name': 'Alice', 'age': 30,}✗ Invalid JSON SyntaxError: Expected double-quoted property name at line 1 column 2 Fix: Use double quotes for keys and strings, remove trailing commas.
Try valid JSON: {"name":"Alice","age":30} — JSON.parse validates the entire document recursively.
Benefits
Find the exact line and character causing the error
Error messages pinpoint the malformed token — missing comma, extra bracket, wrong value type — not just 'invalid JSON'.
Validate API response bodies before parsing
Confirm structure is well-formed before passing to JSON.parse() or json.loads() to prevent unexpected runtime exceptions.
Verify config files before deploying
Validate package.json, tsconfig.json, AWS CloudFormation, and GitHub Actions JSON before applying changes that could break production.
Catch trailing commas and wrong value types
The most common JSON errors — trailing commas after the last element, strings where numbers are expected — are flagged immediately.
Frequently asked questions
What makes JSON invalid?
Common causes: trailing commas, single-quoted strings, unquoted keys, undefined or NaN values, comments (JSON doesn't support comments), and mismatched brackets or braces.
Is there a size limit?
No hard limit, but very large JSON documents may slow down validation. The browser's JS engine handles the parsing, so practical limits are typically in the tens of MB.
Why is JSON stricter than JavaScript object literals?
JSON was designed as a language-independent format. JavaScript's leniency (trailing commas, single quotes) doesn't exist in JSON, which must be parseable by any language's standard library.
Can I validate nested JSON objects?
Yes. JSON.parse validates the entire document recursively, so nested objects and arrays at any depth are all validated in a single parse pass.
What's the difference between JSON validation and JSON Schema validation?
This tool checks syntactic validity (is the JSON well-formed?). JSON Schema validation checks semantic validity (does the JSON have the right structure and data types as defined by a schema?).