No Signal on Monitor? A Complete Troubleshooting Guide

Work through the most useful checks for a monitor showing No Signal, from cable and input selection to graphics output and display detection.

A “No Signal” message usually means the monitor is powered but is not receiving a usable video signal from the selected input. Work from simple physical checks toward software and hardware causes.

1. Confirm the input source

Use the monitor's input/source menu and select the port actually connected to the computer. Auto-detection can fail when several ports are connected.

2. Reseat the cable

Disconnect and reconnect HDMI, DisplayPort or USB-C at both ends. If possible, test another cable or a different port.

3. Verify the computer is outputting video

For a desktop with a dedicated graphics card, make sure the monitor is connected to the graphics card rather than an inactive motherboard video port.

4. Test another display or source

Connecting the computer to another monitor—or the monitor to another device—helps narrow the problem to the display, source or cable path.

5. Check resolution and refresh rate after signal returns

An unsupported timing can cause a blank screen or fallback behavior. Start with a common resolution and refresh rate, then increase settings gradually.

When hardware service is reasonable

If the same monitor shows no signal from multiple known-good sources and cables, or if ports are physically damaged, deeper hardware diagnosis may be needed.

Related tests and guides

Remember: browser diagnostics are observational tools. They can reveal repeatable visual symptoms, but they do not replace laboratory measurement or a technician when hardware diagnosis is required.