OFF (Object File Format) is a geometry definition file format containing the description of the composing polygons of a geometric object. It can store 2D or 3D objects, and simple extensions allow it to represent higher-dimensional objects as well. Though originally developed for Geomview, a geometry visualization software, other software has adapted the simple standard.

The composition of a standard OFF file is as follows:

The four-dimensional OFF format, most notably used by Stella4D, which allows visualization of four-dimensional objects, has a few minor differences:

The vertex, face, and cell data can only be distinguished by the amounts defined at the top of the file. For example, the line "4 0 1 2 3" cannot be distinguished between a tetrahedral cell with faces (0, 1, 2, 3), and a face with vertices (0, 1, 2, 3), if it weren't for the header at the top. Similarly, "3 0 1 2" could be a face with vertices (0, 1, 2) or a 4D vertex with points (3.0, 0.0, 1.0, 2.0).

Comments are marked with a pound sign (#): these are not required to be read by the software.