JSON Lint Online

How to do it

1. Paste JSON suspected of having a parser error into JSON Validator.
2. Read the error message and the position it points to.
3. Fix the issue manually, or send the input through AI JSON Repair to handle the long tail of common mistakes.

What linting catches and what it doesn't

JSON linting checks one thing: does the input parse as valid JSON under the strict spec. It does not check business rules, field meaning, expected types, or whether your numbers are within an allowed range. Those are schema checks, handled by JSON Schema or JSON to Schema. Treat linting as the syntax pass — if it fails, no other check will run reliably.

• Lint = syntax: would JSON.parse accept this string?
• Validate against schema = semantics: do the fields and types match what the API expects?
• Format = readability: does the indentation make the structure visible?

The most common JSON lint errors

Roughly 90% of lint failures we see fall into a handful of patterns. Knowing them by sight saves you a trip back to the documentation.

• Trailing comma — a comma after the last item in [] or {}.
• Single quotes — JSON strings must use double quotes only.
• Unquoted keys — every object key needs to be a quoted string.
• Comments — // and /* */ are JavaScript syntax, not JSON.
• Mismatched brackets — extra or missing { } or [ ].
• Bad escapes — backslashes inside strings need to be paired with a valid escape character.

From lint failure to working JSON

If the validator reports a position, jump there in your editor and look at the character before it — the parser usually flags the next character after the actual mistake. If you cannot spot it, paste into AI JSON Repair, run repair, then run lint again on the cleaned output. Once the validator returns OK, the JSON is safe to feed into a typed parser, JSON.parse or your service's JSON middleware.

Examples

{
          "name": "Ada",
          "role": "admin",
        }

Error: Unexpected token } at line 4 column 1.

{ 'host': 'localhost', 'port': 3000 }

Error: Unexpected token ' at line 1 column 3.

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