"No input detected" is your monitor telling you it is perfectly healthy and simply hearing silence on the input it is watching. The message itself proves the screen works; a broken monitor shows nothing at all, not a helpful status box. So the fault sits in one of three places: the monitor is watching the wrong input, the cable or port between the two devices has failed, or the computer is not sending a picture. Checked in that order, this is usually a five-minute fix, and the most common cause is embarrassingly simple: the input source setting.
Here is the whole diagnosis, ordered from most likely to least.
Read the message like a technician
Error messages are little confessions, and this one confesses a lot: the monitor has power, its electronics work, and it can render text. That immediately clears about half the things people worry about. If you make a habit of taking errors at their literal word, half of tech support becomes easy; we wrote a whole piece on how to read error messages precisely because messages like this one hand you the diagnosis for free.
"No input detected", "no signal", and "check signal cable" are the same statement with different accents: nothing intelligible is arriving on the selected input. Your job is to find out why, starting from the monitor and walking toward the computer.
The fix, in order
Cycle through the monitor's input sources. Press the input or source button on the monitor (or dig it out of the on-screen menu) and step through every option: HDMI 1, HDMI 2, DisplayPort, USB-C, the lot. Monitors watch one input at a time, and auto-detection fails more often than anyone admits. This single step resolves an enormous share of cases.
Confirm the computer is actually on and awake. Fans spinning, power LED steady, not blinking in sleep mode. Tap a keyboard key, click the mouse, or briefly press the power button once to wake it. A sleeping PC sends no signal, and the monitor dutifully reports the silence.
Reseat the video cable at both ends. Unplug from the monitor and from the computer, look into the connectors for bent pins or debris, and plug back in firmly. DisplayPort connectors have a latch; make sure it clicks. Half-seated video cables produce both dead screens and flickering ones.
Make sure the cable is in the right port on the computer. If the PC has a dedicated graphics card, the monitor must connect to the card's ports (lower on the back of the case, horizontal), not the motherboard's video ports (up near the USB cluster). Plugging into the motherboard while a graphics card is installed is a classic, and the symptom is exactly this message.
Swap the cable. Cables die quietly, and a cable can fail while looking factory fresh. Try a known-good cable of the same type. If you switch cable type at the same time (say HDMI to DisplayPort), you learn less from the test, so change one thing at a time.
Try a different port. Move to another HDMI or DisplayPort output on the computer, and another input on the monitor. Individual ports fail on both ends. If the monitor has multiple inputs, this costs you thirty seconds.
Test the monitor against another device. A laptop, a game console, a streaming stick, anything with video out. Picture from another device means the monitor and cable are fine and your computer is the suspect. No picture from anything, on any input, with the cable swapped, finally points at the monitor itself.
Restart the computer with the monitor connected and powered on. This forces a fresh display detection during boot. If you see the manufacturer logo at startup and lose the picture when the operating system loads, the hardware chain works and you have a driver or resolution problem instead; boot into safe mode and reset the display settings from there.
Do not open the computer to reseat the graphics card, or unplug internal connectors, while the machine is plugged into power. If you get as far as suspecting the card itself, shut down, unplug the power cable, and press the case power button once to drain residual charge before touching anything inside. Static and live power both end components.
Which scenario are you in?
| Symptom | Most likely cause |
|---|---|
| Message appeared after moving or cleaning the desk | Cable knocked loose or input changed |
| New PC or new graphics card, first boot | Cable in motherboard port instead of graphics card |
| Works at startup logo, dies when the OS loads | Driver or resolution setting, not hardware |
| Happens only when waking from sleep | Sleep/wake detection quirk, restart and update graphics drivers |
| Second monitor works, first says no input | Bad cable, port, or input selection on the first |
| No device produces a picture on any input | The monitor, at last, is actually the problem |
The "it worked yesterday" cases
When nothing physically changed and the picture is suddenly gone, sleep mode is the usual villain. Some computers fail to re-detect displays on wake, especially over DisplayPort, which is more aggressive than HDMI about announcing disconnections. The workaround is a restart; the longer-term fix is updating graphics drivers, and if the habit persists, switching that monitor to HDMI is a legitimate peace treaty.
The second common case is a resolution or refresh rate the monitor cannot display, set just before the screen went dark. Windows reverts such changes automatically after 15 seconds if you do not confirm, so wait it out. If something has wedged the bad setting in place, boot into safe mode, which uses a basic video mode every monitor accepts, and set the resolution back to something sane.
If your setup involves a TV rather than a monitor, the same logic applies but the failure modes shift toward the cable and handshake side; our companion guide on HDMI showing no signal walks that path, including the copy-protection handshake quirks that TVs and receivers add to the party.
Adapters, docks, and switches: the extra suspects
Every box between the computer and the monitor is another place for the signal to die, and modern desks have more of them than ever. If your setup includes a USB-C dock, an HDMI-to-DisplayPort adapter, a KVM switch, or a splitter, treat that device as a full suspect and test around it: connect the computer straight to the monitor with a single plain cable and see whether the picture returns. If it does, the middleman is guilty, and the fix is usually its power supply, its own firmware update, or replacement.
Adapters deserve particular suspicion because they have direction. An HDMI-to-DisplayPort adapter and a DisplayPort-to-HDMI adapter look identical and are not interchangeable; using one backward produces a clean, confident "no input detected." Passive adapters also have version and resolution limits, so an adapter that worked with an old monitor can fail silently on a new high-refresh one. When buying, match the adapter's stated direction and maximum resolution to your actual hardware.
Laptop users with USB-C should check one more thing: not every USB-C port carries video. Many laptops only output display signal from specific ports (often marked with a small lightning bolt or display symbol), and plugging the dock into a charge-only port yields a black monitor and no error anywhere. Your laptop's manual states which ports carry DisplayPort Alt Mode; it takes one minute to check and settles the question permanently.
When it's the computer not sending anything
If another device gets a picture on the same monitor and cable, your computer is the one staying quiet, and the question becomes whether it is failing to boot or just failing to output.
Listen and look. A single short beep (on PCs that beep) and normal fan behavior suggest the machine boots fine and only the video path is dead: suspect the graphics card, its port, or its power connectors. Repeating beep patterns, or fans that roar at full speed forever, suggest the computer itself is failing its startup self-test, which is a different repair.
From here on, the method matters more than any single trick: change one variable at a time, test after each change, keep notes. That discipline is the entire secret of our universal troubleshooting method, and it is what stops you from swapping three things at once and never learning which one was guilty.
Frequently asked questions
What does no input detected actually mean?
The monitor has power and works, but no video signal is arriving on the input it is currently watching. It is a status report, not an error in the monitor. The cause is the input selection, the cable, the ports, or a computer that is not sending video.
Why does my monitor say no input when the PC is on?
Most often the monitor is set to the wrong input source, the cable has failed or worked loose, or the cable is plugged into the motherboard instead of the graphics card. A powered-on PC can also be sitting in sleep or failing its boot process while fans still spin.
How do I know if the monitor or the computer is the problem?
Connect another device (laptop, console, streaming stick) to the same monitor and cable. If it shows a picture, the monitor and cable are fine and the computer is at fault. If nothing produces a picture on any input with a swapped cable, the monitor is the problem.
Why does no input detected appear after sleep?
The computer sometimes fails to re-detect the display when waking, a quirk most common over DisplayPort connections. Restarting restores the picture. Updating graphics drivers usually cures the habit, and switching to HDMI is a reasonable workaround if it persists.
Can a bad HDMI or DisplayPort cable cause no input detected?
Absolutely, and the cable can look flawless while doing it. Cables fail from bending, crushing under desks, and cheap manufacturing. Swapping in a known-good cable is a thirty-second test and belongs early in any diagnosis.
My new PC says no input detected on first boot. What now?
Check that the video cable goes into the graphics card's ports, not the motherboard's. On a machine with a dedicated card, the motherboard video outputs are typically disabled. Also confirm the card's power cables are connected and the card is fully seated.
When to stop and swap hardware
You have earned the right to blame hardware once you have cycled every input, reseated and swapped the cable, tried a second port, tested the monitor with another device, and restarted the computer with everything connected. At that point the remaining suspects are the monitor's electronics or the computer's video output, and your other-device test already told you which. Monitors under warranty should go back rather than to a repair bench, since panel repairs rarely make financial sense. And if it turned out to be the input button all along, your secret is safe with us.