This is an umbrella term for both cross_eye_stereogram and wall_eye_stereogram. A side-by-side stereogram is where the image is rendered from the perspective of two "cameras", and both perspectives are juxtaposed horizontally.

• cross_eye_stereogram - to perceive the 3D effect, the viewer must view these with their eyes crossed, such that the right eye focuses on the left image, and the left eye focuses on the right.

• wall_eye_stereogram - to perceive the 3D effect, the viewer must view these with their eyes parallel, such that the right eye focuses on the right image, and the left eye focuses on the left.

The two formats can be converted by simply swapping the sides in an image editor such as Gimp or Photoshop.