JSON Validator

Validate JSON before it breaks your app

A single misplaced comma is enough to make JSON.parse(), json.loads() or a configuration loader fail. This validator checks your document against the official JSON standard (RFC 8259 / ECMA-404) and, when something is wrong, explains what is wrong and where: for example Trailing comma is not allowed in JSON objects (line 7, column 1). Different browsers word their native errors differently, so the tool uses its own parser to give the same precise message everywhere.

When the JSON is valid you also get a short report: the root type (object or array), the total number of keys, the maximum nesting depth and the size in bytes — handy when you need to stay below an API payload limit.

How to validate JSON

1. Paste JSON into the input box or upload a file. Validation runs automatically as you type.
2. Read the status bar: green means valid, red shows the error with line and column.
3. Fix the reported problem and the result updates immediately.

What the validator checks

• Strings and property names use double quotes and valid escape sequences (\n, \", \u00e9…).
• No raw line breaks or tabs inside strings.
• Commas between items, and no trailing commas.
• Numbers have no leading zeros, and there is no NaN, Infinity or undefined.
• Only one top-level value, with nothing after it.

Example error

{
  "name": "Asha",
  "age": 31,
}

Trailing comma is not allowed in JSON objects (line 4, column 1)

}
^