While it may not be strictly necessary to book Duomo Museum tickets in advance, it is highly recommended, especially during peak tourist seasons. Booking in advance allows you to secure your entry, skip long lines at the ticket counters, and plan your visit more efficiently. Additionally, during busy times, there is a risk of tickets selling out for specific time slots. Booking online in advance provides convenience and ensures a smoother experience, allowing you to focus on exploring the museum's treasures without unnecessary delays.