pillarboxing

Pillarboxing is the presence of vertical black bars on the left and right sides of an image or video to preserve its original aspect ratio when displayed inside a container that is wider than the content. The effect is named for the “pillars” created by the bars.

It occurs whenever the source content has a narrower aspect ratio than the display format. A common example is 4:3 television or film shown on a 16:9 screen, which leaves black bars on the sides to avoid stretching the picture. Conversely, displaying widescreen material on very wide displays can produce different results depending on how the image is mapped to the screen.

Technically, pillarboxing results from the need to preserve the source’s aspect ratio during scaling. When the display area is wider than the content, the image is scaled to fit height (or width, depending on the system) and the remaining horizontal space is filled with black. This contrasts with letterboxing, where the bars appear at the top and bottom for content that is wider than the display’s aspect ratio.

Impact and alternatives: pillarboxing preserves fidelity and composition but reduces the image area, which can affect immersion. Alternatives include cropping (removing portions of the sides) or stretching (distorting the image to fit). In practice, pillarboxing is common in broadcasting, streaming, and video games when aspect ratios do not match the display or when legacy content is preserved.

Related terms include letterboxing, windowboxing, cropping, and anamorphic transfer.