The C++ program hybtil constructs free hybrid planar tiles (polyforms) composed of equilateral squares and triangles. They are free in the standard polyomino sense that rotations, translations and reflections of the shape represent the same tile. They are hybrid because they are composites of connected, non-overlapping monotiles that have two distinct base shapes: squares and equilateral triangles; the squares and triangles have the same (unit) edge lengths.