No, you do not need to provide a license plate number when making a parking reservation for Muir Woods. Reservations are tied to the name and email address used at checkout, not a specific vehicle.
However, please ensure that you bring a copy of your voucher (printed or digital) to scan upon arrival. If you have any issues retrieving your voucher, parking attendants can look up your reservation using the 9-digit barcode number provided in your confirmation email.