Yosemite National Park has 13 popular campgrounds, of which up to seven are on a reservation system. From April through September, reservations are essential and even the first-come, first-served campgrounds usually fill by noon (often earlier) from April through September.
Reservations are required all year for Yosemite Valley's car campgrounds and summer through fall for Hodgdon Meadow, Crane Flat, Wawona, and half of Tuolumne Meadows. Campground reservations are available in blocks of one month at a time, up to five months in advance, on the 15th of each month at 7 am Pacific time. Be aware that nearly all reservations for the months of May through September and for some other weekends are filled the first day they become available, usually within seconds or minutes after 7 am! For your best chance of getting a reservation, be sure your clock is set accurately and start the first few steps of the reservation process at www.recreation.gov before 7 am Pacific time. You can find more help making reservations and other frequently asked questions.
From late May through early September, space at Camp 4 is available only by daily lottery one day in advance.