JSON Validator

Paste JSON and see immediately whether it is valid. Errors are reported with a line and column so you can jump straight to the problem.

What counts as valid JSON

This validator uses the browser's native JSON.parse, which implements the strict grammar from RFC 8259. That means:

• Keys and strings use double quotes only.
• No trailing comma after the last item of an object or array.
• No comments of any kind.
• Numbers cannot have leading zeros, a leading +, or be NaN/Infinity.
• Only true, false and null are bare words.

Common errors and what they mean

Unexpected token '}' / Expected double-quoted property name

Almost always a trailing comma: {"a": 1,}. Remove the comma before the closing brace or bracket.

Unexpected token ' (single quote)

Strings in JSON must use double quotes. Replace 'value' with "value".

Unexpected end of JSON input

The document stops early — a missing closing } or ], or the text was truncated when copied from a log.

Unexpected token / in JSON

A comment. JSON has no comment syntax. Delete it, or use the formatter, which strips comments and emits clean JSON.

See the full list in the guide: JSON syntax errors explained.

Privacy

Validation happens entirely in your browser. Nothing is sent to a server, so it is safe for tokens, customer data and internal payloads.