NorthlaneSeveral of the most visited parks now use timed-entry or vehicle reservations during peak season. The rules change year to year, so we treat the official NPS page and Recreation.gov as the only sources that count.
The key planning move is to put reservation parks on fixed days and let everything else flex around them. Arrive before the reservation window opens and you often do not need a ticket at all, but plan on it only as a bonus.
We include release dates and booking reminders in every itinerary that touches a reservation park, so nothing depends on remembering at midnight.