The PC starts, but the monitor shows a box saying “Input Not Supported,” “Out of Range,” or “Signal not supported,” and the desktop never appears. When a Windows 10 monitor says input slot88 not supported, the PC is sending a resolution or refresh rate the monitor cannot display.

This usually happens after changing display settings, connecting a different monitor, or running a game that switched to an unsupported mode and crashed before switching back.

The PC itself is working. The monitor simply refuses the signal format.

Getting Windows back to a safe display mode solves the problem, and there are several ways to do it even when you cannot see anything.

Possible Causes

The monitor rejects the signal for these reasons:

• The resolution or refresh rate is higher than the monitor supports.
• A game set an unsupported display mode for the desktop.
• The PC remembers settings from a previous, more capable monitor.
• The cable or adapter cannot carry the selected mode.

Monitors often show the message for a few seconds and then go dark, which makes it look like a hardware fault.

High refresh rates are a frequent trigger. A gaming monitor may support 144 Hz over DisplayPort but only 60 Hz over an older HDMI cable, so the same setting can work on one cable and fail on another.

Quick Fixes to Try First

Let Windows fall back to a safe mode.

1. Wait 15 seconds after changing display settings. Windows reverts automatically if you do not select “Keep changes.”
2. Press Windows + Ctrl + Shift + B to reset the graphics driver.
3. Press Windows + P, then the down arrow and Enter, to cycle display modes.
4. Connect a different monitor or TV to reach Display settings and lower the resolution and refresh rate.
5. Try a different cable or port.

If you can see the desktop on another screen, set the problem monitor to its recommended resolution and 60 Hz.

Advanced Steps for Stubborn Cases

Use low-resolution mode.

1. Turn the PC on and off at the logo three times to reach the recovery menu.
2. Choose Troubleshoot > Advanced options > Startup Settings > Restart.
3. Press 3 for “Enable low-resolution video.”
4. In Windows, open Display settings and set the recommended resolution and a supported refresh rate.
5. Restart normally.

If a game caused the problem, edit its settings file or start it in windowed mode before playing again.

Before You Go Further: Keep Your Files Safe

Forcing the PC off is acceptable for reaching recovery, but avoid repeating it more than necessary. Display settings changes do not affect files.

Conclusion

“Input not supported” means the PC is sending a mode the monitor cannot show. Wait for the automatic revert, use another screen, or boot with low-resolution video and choose supported settings.