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Fix a Chromebook that has display that has wrong underscan

We'll adjust overscan/underscan in Settings or the monitor OSD, rule out resolution and cable, or tell you when to call support.

Troubleshooting · Home maintenance
5–15 min
What you'll need
  • Chromebook
  • External monitor and cable (if using one)
Step 1 of 7

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Steps

Goal: Confirm the underscan symptom, adjust overscan or display size, then rule out resolution, cable, or hardware issues.

  • Check whether black borders appear around the image—the picture does not fill the screen.
  • Good: You have confirmed underscan. Proceed to Built-in display or External display.
  • Bad: Unclear—open Settings > Device > Displays and check the current settings.

Built-in display

Goal: Adjust overscan or display size on the built-in screen.

  • Click the status area (clock), then the gear icon. Settings > Device > Displays.
  • Look for overscan, picture size, or display size. Move the slider to fill the screen. If no option exists, set Resolution to the recommended value.
  • Good: The image fills the screen. Done.
  • Bad: No option or settings do not stick—restart; if still wrong, Powerwash or call support.

External display

Goal: Adjust picture size on the external monitor using its OSD.

  • Settings > Device > Displays. Select the external display. Set resolution to recommended.
  • Use the monitor OSD (buttons on the monitor). Look for picture size, aspect ratio, overscan, or scaling. Adjust until the image fills the screen.
  • If the image still has borders, try a different HDMI or USB-C cable. A bad cable can cause underscan.
  • Good: The image fills the screen. Done.
  • Bad: Monitor OSD and cable checked, still wrong—call support.

Restart and Powerwash

Goal: Reset display state if settings do not stick.

  • Restart the Chromebook. Recheck Settings > Device > Displays. If underscan was stuck, restart may fix it.
  • If settings keep reverting, Powerwash may help. Settings > Advanced > Reset settings > Powerwash. Back up your data first. After Powerwash, set display options again.
  • Good: Settings persist. Done.
  • Bad: Settings still revert—call support.

When to get help

Call support if:

  • No overscan/underscan option exists and the monitor OSD does not fix it.
  • Settings do not stick after restart or Powerwash.
  • The image stays wrong after trying all steps.

Verification

  • The image fills the screen with no black borders.
  • Resolution is set to recommended in Settings > Device > Displays.
  • For external displays, the monitor OSD is set correctly.
  • Settings persist after restart.

Escalation ladder

Work from the device outward. Stop when the problem is fixed.

  1. Overscan and resolution Adjust overscan/display size; set resolution to recommended.
  2. External monitor OSD Use monitor buttons to adjust picture size.
  3. Cable and restart Try different cable; restart Chromebook.
  4. Powerwash Powerwash if settings do not stick.
  5. Call support No option to fix or display stays wrong.

What to capture if you need help

Before calling support or posting for help, have these ready. It speeds everything up.

  • Chromebook model
  • Built-in or external display
  • Overscan/display size settings
  • Steps already tried

Is the problem on the built-in display or an external monitor?

Built-in and external displays use different settings.

Check Settings > Device > Displays. If you use an external monitor, select it. Built-in: adjust overscan or display size in Settings. External: check Chromebook and monitor OSD.

Built-in External

You can change your answer later.

Is there an overscan or display size option?

Some Chromebooks have overscan in display settings.

Settings > Device > Displays. Look for overscan, picture size, or display size. Option exists: adjust it to fill the screen. No option: set resolution to recommended; restart. If still wrong, Powerwash or call support.

Yes No

You can change your answer later.

Adjust overscan

Move the overscan or display size slider to fill the screen. Restart if needed. If settings stick, you are done. If they revert, Powerwash or call support.

Done

Set resolution to recommended

Set Resolution to the recommended value. Restart. If the image fills correctly, done. If not, Powerwash or call support—built-in may not support underscan adjustment.

Done

Does the monitor OSD have picture size or overscan?

External monitors often have OSD controls.

Use the monitor buttons (OSD). Look for picture size, aspect ratio, overscan, or scaling. Adjust until the image fills the screen. Fixed: done. Not fixed: check resolution and cable.

Yes No

You can change your answer later.

Try different cable

A bad HDMI or USB-C cable can cause underscan. Try a known-good cable. Set resolution to recommended. If still wrong, call support.

Done

Underscan fixed

Image fills the screen. No further action needed.

Done

Reviewed by Blackbox Atlas

Frequently asked questions

Why would a Chromebook display have wrong underscan?
Underscan means the image is smaller than the display—black borders around the edges. Often caused by overscan/underscan settings, wrong resolution, or external monitor OSD. Adjust in Settings or on the monitor.
Can I fix wrong underscan myself?
Yes. Settings > Device > Displays. Look for overscan or display size. For external monitors, use the monitor OSD to adjust picture size. Check resolution and cable.
When should I call support for wrong underscan?
If no overscan/underscan option exists and the monitor OSD does not fix it, or the image stays wrong after Powerwash. The display or cable may be faulty.

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