Complete JSON Syntax Error Reference

Diagnosing Common JSON Syntax Errors

JSON parse errors occur when data fails strict RFC 8259 syntax validation. Because JSON is commonly passed through network payloads, single-character syntax errors can break client applications.

Most Frequent Error Types:

• SyntaxError: Unexpected token: Triggered by single quotes, unquoted keys, or missing colons.
• Trailing Comma in Array or Object: Strict JSON disallows commas after the final element.
• Unescaped Control Characters: Newlines and raw tabs inside strings must be escaped as \n or \t.

// Invalid JSON
{
  'name': 'Alice',
  "roles": ["admin",],
}

// Valid JSON
{
  "name": "Alice",
  "roles": ["admin"]
}