JSON Validator
Validate and check JSON syntax. Detailed error reporting with line numbers. Free.
How to use the JSON Validator
Common JSON mistakes
The classic errors: trailing commas ([1, 2, 3,] — JSON doesn't allow them, unlike JavaScript), single quotes (must be double), unquoted keys ({name: "a"} is invalid — keys must be quoted strings), and undefined or function values (JSON only supports strings, numbers, booleans, null, objects and arrays).
Strict standard
JSON is defined by RFC 8259 / ECMA-404. Numbers cannot have leading zeros (other than 0 itself), comments are forbidden, and the top-level value must be an object, array, string, number, boolean or null. This validator follows the strict standard — the same as JSON.parse in every modern browser.
RFC 8259 (the current JSON spec) requires UTF-8 encoding for JSON exchanged between systems. It also explicitly bans trailing commas, comments, and single-quoted strings — which is why valid JavaScript object literals often aren't valid JSON.