JSON Validator

Paste any JSON. The status line says ✓ valid or ✗ with the parser's error message and offset.

What "valid JSON" means

JSON is defined by RFC 8259. Valid JSON consists of:

• An object ({...}) or array ([...]) at the top level — or any single value (string, number, boolean, null), per RFC 8259.
• Object keys as double-quoted strings.
• Values: object, array, string (double-quoted), number, true, false, or null.
• No trailing commas.
• No comments.
• No NaN, Infinity, or -Infinity — JSON has no IEEE-754 special values.
• Strings must be valid UTF-8 (or Unicode-escaped via \uXXXX).

What's NOT valid JSON

Common things people confuse for JSON:

• JavaScript object literals — {name: "Alice"} is JS, not JSON. Keys need quotes.
• JSONC / JSON5 — comments and trailing commas are convenient but technically not JSON.
• NDJSON / JSON Lines — multiple JSON values separated by newlines. Each line is JSON; the whole file is not.
• Python dict repr — {'name': 'Alice'} uses single quotes; not JSON.
• Anything from a templating system that interpolated unescaped data — {"name": "{{user.name}}"} may have unescaped quotes inside.

Reading parser errors

Browser JSON.parse errors are concise. Examples:

Validating in code

// JavaScript / TypeScript
function isValidJson(s) {
  try { JSON.parse(s); return true; }
  catch { return false; }
}

// Python
import json
def is_valid(s):
    try: json.loads(s); return True
    except json.JSONDecodeError: return False

// Bash with jq
echo "$INPUT" | jq empty 2>/dev/null && echo valid

// Go
import "encoding/json"
var v interface{}
err := json.Unmarshal([]byte(input), &v)

Beyond syntactic validation

"Valid JSON" only means parseable. To enforce shape (this object must have a name string and an age integer), use JSON Schema or a runtime validator like Zod (TypeScript) or Pydantic (Python).