35mm has been the standard theatrical exhibition format since the early 20th century. As the name implies, it is 35mm in width.
For much of the 20th century, 35mm was used for production, editing, distribution, and projection. In its most typical iteration, each frame is four perforations in height. It can accommodate multiple aspect ratios when used in conjunction with different lenses and aperture plates: 1.33:1, 1.37:1, 1.66:1, 1.85:1, and 2.35:1.
There are other variants, including VistaVision (eight perforations per frame, running horizontally), dual-strip polarized 3-D (two 35mm prints running on two projectors, interlocked), Techniscope (two-perf negative, optically printed to four-perf Cinemascope), Super 35 (three-perf negative, printed to four-perf print with an anamorphic squeeze or a hard matte).