JSON Validator

Check whether JSON is valid and see exactly where it breaks — line and column of the first syntax error, such as a trailing comma or a missing quote. Nothing is uploaded; runs in your browser.

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About JSON Validator

JSON Validator checks whether your JSON is syntactically valid and, if not, tells you exactly what is wrong and where — the line and column of the first error, such as a trailing comma, a missing quote or a stray character.

It also warns about duplicate keys in the same object, which are technically allowed but usually a mistake, because most programs silently keep only the last value. Everything runs locally in your browser — the text you paste is never uploaded.

How to use JSON Validator

  1. Paste your JSON or upload a .json file.
  2. Press Validate.
  3. Fix the reported line, then validate again until it says Valid JSON.

Key features

  • Exact line and column for syntax errors
  • Duplicate-key warnings
  • Large files handled locally
  • Pairs with JSON Formatter for fixing layout

Example

A trailing comma — the most common JSON error — reported with its position.

Input
{
  "name": "Asha",
  "city": "Surat",
}
Result
Invalid JSON: trailing comma before "}" (line 4, column 1)

When to use JSON Validator

  • Checking a hand-edited config file before deploying it.
  • Finding why an API rejects your request body.
  • Confirming that exported data is valid JSON before importing it.

Tips and common problems

  • Trailing commas, single quotes and comments are the most common errors.
  • When the error points to the last line, look for an unclosed bracket or quote earlier.
  • Duplicate keys are allowed by the syntax but usually a mistake — the tool warns you about them.

Frequently asked questions

Trailing commas after the last item, single quotes instead of double quotes, unquoted keys, comments, and missing commas between items. JSON allows none of these.