How to Adjust Projector Overscan and Underscan Settings

What overscan and underscan mean

Overscan enlarges the projected image so that the edges extend beyond the visible screen area. It was originally used with old analog broadcasts that had noisy edge content. On a digital projector, overscan can appear as a crop that cuts off subtitles, channel logos, or the edges of a computer desktop.

Underscan does the opposite. It shrinks the image so that a black border surrounds the picture on all four sides. Underscan is sometimes called overscan off, screen fit, or dot-by-dot, depending on the projector brand. You might choose underscan when you want to see the complete frame including the outermost pixels, or when the projection surface has a slightly smaller visible area than the projector's panel.

Both controls change how much of the source signal is shown. With overscan at zero, the projector displays the full image from the HDMI or other input. Increasing overscan hides the outer edges and enlarges the center content. This is not the same as zoom, which scales the entire image, because overscan often works by cropping rather than resampling.

Where to find the controls

Most projectors place overscan and underscan settings in the image or display portion of the on-screen menu. The exact wording differs by brand: some call it overscan, others use screen fit, aspect ratio, or expand. On many models it appears as a percentage, such as 0 percent, 5 percent, or 10 percent.

If the projector has a zoom adjustment, keep it separate from overscan. The zoom lens or digital zoom changes the size of the entire projected area, while overscan crops the source. You will get the cleanest result by first setting zoom so the image is slightly larger than your screen, then reducing overscan to show the complete picture.

A few projectors do not expose overscan at all. In that case, you can still fix a cropped image by adjusting the source device. Many streaming devices, computers, and set-top boxes have their own screen fit or display area controls. See the next sections for the order of adjustments.

• Open the projector's on-screen menu and look under Picture, Display, or Screen settings.
• Search for terms like overscan, underscan, screen fit, or aspect ratio.
• Some projectors include a test pattern or guide lines to help you see the edges.
• If the projector has no overscan control, adjust the output of the source device instead.

Step-by-step adjustment

Start with a test pattern that has a white border or corner markers. Free test patterns are available as videos, image files, or from some projector menus. You want a pattern that clearly shows whether the edges of the frame are being cut off.

Set the projector to show the test pattern from the source you will use most, such as a streaming device or a PC. If you use multiple sources, check each one because overscan can differ between them. HDMI signals from a set-top box often arrive with overscan already applied, while a PC connection sends a full-frame signal.

Reduce or turn off overscan on the projector first. If the image now shows a black border around the test pattern, you have corrected the crop. If the image is still cropped, move to the source device and look for its own display area or zoom setting. Reduce it until the full test pattern is visible.

After fixing overscan, use the projector's zoom and any lens shift to position the image exactly on your screen. Avoid relying on keystone correction to fix edge issues that actually come from overscan. Keystone alters the geometry, while overscan and zoom change the content area. For more on keystone, see Keystone Correction.

Adjusting the source device

The HDMI specification defines how video and audio are carried between the source and the display. It does not require a specific overscan behavior, so each device maker decides how much overscan to apply. That is why the same projector can show a complete image from one source and a cropped image from another.

On a PC, the overscan control is usually in the graphics or display driver. Look for scaling options that include overscan, underscan, or desktop size. On a Mac, the display settings or the non-native resolution settings may provide an adjustment for the image edges.

On a streaming device, the setting is often called display area, screen fit, or over-scan. Set it to fit the full screen or to the largest visible area. Some devices detect the display type automatically and choose the wrong setting when connected to a projector, because a projector is not always recognized as a large display. For more on connections, see Projector Inputs Explained.

Aspect ratio and resolution considerations

Overscan can interact with the projector's aspect ratio setting. If the source is 16:9 and the projector is set to a different aspect ratio, some edges may be cut even with overscan at zero. Check that the aspect ratio matches the source signal before adjusting overscan.

When the source resolution is lower than the projector's native panel, the projector scales the image. This scaling usually does not crop, but some projector modes add a zoom that behaves like overscan. For example, a native 4K projector showing 1080p content might have a mode that enlarges the source to fill the panel. On most models, you can disable this and show the 1080p image without any cropping. See Native vs Supported Resolution and Projector Aspect Ratio for background.

Underscan is also useful when your projection screen does not match the projector's aspect ratio. Shrinking the image slightly can keep the entire visible area within a screen that is a few inches off, instead of changing the zoom and recomputing the image size.

When overscan is desirable

There are a few cases where a small amount of overscan is useful. Some TV broadcast streams still include edge artifacts or a subtly corrupted border that you do not want to see. A few channels also have scrolling text that touches the edge, which can be hidden with a small overscan crop.

Overscan can also hide slight edge misalignment when the projector is mounted and the image is not perfectly centered on the screen. It is not a replacement for proper mounting, but it can mask a small deviation. For projector placement and alignment, see Projector Placement and How to Align a Projector Image on a Wall or Screen.

For gaming or PC use, keep overscan at zero unless you have a specific reason to crop. A cropped desktop can hide parts of the taskbar, game HUD, or application windows. If you need to enlarge the image, adjust the zoom and if the projector has a digital zoom, use that before relying on overscan.

What to pick for your use

Questions

What is the difference between overscan and zoom on a projector?

Zoom (optical or digital) changes the size of the entire projected image. Overscan crops the outer edges of the source and enlarges the center portion. With zoom you still see the full frame if the image is within the screen; with overscan you lose the outer pixels.

Why is my projected image cut off at the bottom?

This is usually overscan, a cropped source, or an aspect ratio mismatch. First reduce overscan on the projector. If the cut remains, look at the source device settings. If the image is also not rectangular, keystone or lens shift may be involved. See Keystone Correction.

Can overscan damage the projector lamp or panel?

No. Overscan is a digital picture adjustment. It does not affect the lamp, panel, or light source. It only changes which pixels from the source are visible on the screen.

Do all projectors have overscan settings?

No. Many projectors include an overscan or screen fit setting, but budget models especially may not expose it. In that case, you can adjust the source device. Some models also apply overscan only through an aspect ratio mode, so try each aspect mode to see if it changes the visible edges.

Should I use overscan on a 4K projector?

For 4K content and gaming, keep overscan off so you see the full frame. A small overscan was common with old broadcast content, but 4K video, streaming, and PC sources are meant to be shown edge-to-edge. If the projector applies overscan automatically, look in the input or screen settings for a fit or dot-by-dot mode.

How do I know if my projector is overscanning?

Use a test pattern with a border. If the border is not visible on all four sides, the image is cropped. You can also open a computer document with text at the page margin: if the margin is missing, overscan is active.