What does “No Signal” mean?

"No Signal" is a message coming not from your computer, but from your display device, indicating that it has nothing to display. I'll review possible causes.

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I  just started to get a “No Signal” message when trying to start up. When I push the Panic button on the tower, it starts. Everything works normally after the start. What’s going on?

This message, and several others like it, confuse many people.

The reason for the confusion is that the message isn’t actually coming from your computer at all.

And on top of all that, it might, or might not, indicate that there’s a problem.

PCs and display devices

Your desktop computer is typically connected to an external display device that’s variously referred to as the monitor, screen, or display. It is not “the computer”, since by itself, the display can do almost nothing. It’s only when connected to your computer that a display serves a purpose.

The video card or video circuitry inside of your computer turns the bits and bytes that represent the image you see on your screen into information that travels along the cable connecting your computer to the display. There are various types of cables and video interfaces, ranging from the older “VGA” style to the newer Digital Video Interface (DVI) and the increasingly popular High-Definition Multimedia Interface (HDMI).

Even if you’re using an all-in-one computer or a laptop with a built-in display, this is all still present, though often using different interface technologies and hidden from view.

Each of these interfaces transmit the information about what should be displayed from the computer to the display.

Monitor and Computer

The information traveling along that connection is typically referred to as the “signal”1.

And therein lies the clue…

No signal

The “No Signal” message does not come from your computer – it’s generated by the display itself.

Disconnected Monitor and Computer

All it means is that the monitor is not receiving a video signal from the computer.

That’s all.

Possible causes

That’s a pretty simple explanation. In fact, from the display’s point of view, it’s a pretty simple situation: it’s expecting a signal, telling it what to display, and it’s not getting it. So it displays a message on its own to tell you what’s up.

Like so many “simple” situations, there are many, many possible causes:

  • The display is on, but the computer is not.
  • The cable connecting the computer to the display has become disconnected.
  • The cable connecting the computer to the display is faulty.
  • The display has multiple inputs, and the wrong one is selected.
  • The computer has multiple display outputs, and the one the actual display is connected to is not enabled. (This is very common when trying to get an external display to work with a laptop.)
  • The computer is in standby or hibernate mode, and has turned off its display signal.
  • The computer has crashed in such a way that it’s just not trying to display anything.
  • The computer is broken in such a way that it cannot boot.
  • And, of course, the display itself could be broken.

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It’s also not uncommon, and completely normal, for a display to show “No Signal” for some period of time while your computer boots up. Very often the computer’s display adapter will temporarily stop trying to display anything as it is configured for use by Windows.

As you can see, there are many possible causes for a simple error message.

When faced with this situation (and I have been!), I check to make sure that everything is on (it’s so embarrassing when it’s not :-) ) and that the cable is properly connected. If that doesn’t resolve it, then I move on to trying another cable or display, and finally, attempting to diagnose whether the PC is working at all.

Display messages

Computer displays have become sophisticated devices in their own right and may often display messages of their own. It’s important to realize that these messages are not coming from your computer at all; they’re being presented by the display.

In the case of “No Signal”, it may be the only thing on the screen.

Other display-generated messages will often appear “on top of” whatever else your computer is displaying.

Understanding what they look like and what steps need to be taken means becoming familiar with your monitor’s options and controls – something completely separate from the computer itself.

This is an update to an article originally posted : May 19, 2011
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Footnotes and references

1: Technically, “signal” refers to any electronic signalling mechanism that carries information. It commonly refers to analog signals, like radio, TV, and the video signal carried over the VGA interface. It applies to digital information as well – in some cases, because digital information is transmitted using otherwise analog media.

Comments

  1. Bob S

    This happens to me almost every time the computer comes out of standby (Windows XP). I think it means the monitor was off and first turned back on, but the computer is not sending any video just yet — it’s still coming back up from standby. After a few seconds the screen lights up and all is well.

  2. Mike

    I guess the question is, what is the “panic button” on the tower, and how would it change the No Signal indication? “Startup” doesn’t differentiate between Bootup, or coming out of Hibernate or Standby. However, like Bob S stated, it’s most likely a short term indication that will correct itself after several moments for the video card to start sending out display data again.

  3. Keef

    “No Signal” can just be a simple problem that as the PC “wakes from sleep” and the video card doesn’t wake up fast enough. So the monitor reports no signal. this can sometimes be resolved by just turning the monitor off and on again to flush the message. or by setting the PC bios to “refresh video bios on wake from sleep” STR 3 or some simular bios option found on most modern PCs

  4. Eugen

    I had this problem with the “No input signal”, but in another way: I had to recover the C partition from a backup, the backup program started, and after 5 minutes a had this message on my monitor. I could not see anymore what is the status of the recovering process… I had a shock, believe me… I found later where the problem was: a setting in W7 to stop the monitor after 5 minutes of inactivity… but until I found that, I really wanted to buy a gun to shot the video card…

  5. NWReader

    I had this problem when I had to buy a new monitor. I kept thinking it was because the new monitor was bad and after 3 upgraded monitors later it turned out I really did need a new video card. It’s very interesting to see all the different reasons why this might happen. Thanks for all your help, Leo and all responders!

  6. Bernard schwab

    Had this problem for weeks.
    My video card had an outdated revision.
    Updated it and all problems are gone.
    Video card:
    NVIDIA GeForce FX 5200
    Windows XP

  7. Margaret Louk

    My monitor has given a no signal notice since I bought it. The monitor came with the package and has a built in speaker. They sounded like an old transistor radio (yes I am that old). So disabled the speakers in the monitor and attached my Bose speakers to the computer and I have great sound. It just keeps giving me the same signal.

  8. Caroline

    I use Windows XP Pro on a desktop. A few weeks ago after getting a Blue Screen of Death, I have the same problem and it’s driving me crazy! I’ve checked just about everything I can check, including running several scans of various types and many of the suggestions in this article, including replacing the cable with a brand new one, but the only way I can get my monitor to display anything is to press F8 when booting up and hope I can select “Last known good configuration” before that menu vanishes and the screen goes black again. I have to try several times before the menu stays visible for long enough to do so. Once it’s in Windows it’s fine, I have no problems at all so if I’m going to be afk for a few hours or so I leave it on rather than go through all that hassle again. Unfortunately, I’m not a hardware expert so I’m reluctant to take the PC apart and I wouldn’t know what to look for anyway.

  9. wim

    Hello

    I get the “no signal” on my screen only after gaming.
    I get no display what so ever so I am forced to use the reset button
    so my problem is
    computer has crashed in such a way that it’s not trying to display anything.”

    Would it be possible to explain this to me, in what way could the pc crash with this problem? It’s not trying to display anything, so is it my videocard or something else?

    Regards

    There’s no simple answer. Many different types of crashes could cause video to be turned off.

    Leo
    18-May-2012
  10. Mark Jacobs

    Another possible cause for this could be a video driver problem. Coincidentally, I’m in the middle of a similar problem. I’m trying to revive an old XP machine. Everything works fine except the screen resolution. When I try to change it, I get a message from my monitor that it requires a 1920X1080 resolution. It bypassed the usual reverting to the previous resolution Windows normally gives. So, I rebooted using the “Go back to a previous configuration which worked” and get the screen to work again. (As Leo said, System Restore is great when it works) Then I went to the Asus website and downloaded the driver for that net top. I installed it and when it rebooted, I got that same warning again. I booted again with the go back option and it worked but again with the bad resolution. Now I’m trying to figure out if somehow the driver is not compatible with my monitor or it’s simply that it’s not the correct driver even if it is the one Asus offers for that machine with XP.

      • Mark Jacobs

        Funny you should say that. Well, not exactly, I installed Mint Linux :) Everything just works, and all the programs I need are already installed with the OS.

  11. Tony Mahon

    Hi Leo and many thanks for providing such a great IT knowledge base and all for free ! Well I have bought some of your publications!
    Two things – Any idea why Firefox always marks your weeklies with a dire red warning of spam? I have got it set to warn me of what it thinks is spam, I just wondered why Firefox gets it wrong. The second thing is that , although I have already subscribed to your weekly offerings, the adware pops up within the email and asks me if I would like to subscribe with offerings of one of your publications is I do so.
    Kind Regards,
    Tony

  12. Jim Sweeney

    You say several times that “the message is coming from the device (display or monitor).
    If the cable is disconnected – how can the monitor initiate the message.
    Isn’t it the video card or the driver that is initiating the message?

    • Connie

      The monitor is actually capable of displaying the message all by itself if it is unplugged from the computer. It does need to be plugged into power however!

  13. Andrew

    Have an ASUS desktop, purchased a new monitor on the strength of the “No Signal’ message believing my old monitor had had it. Didn’t resolve anything, although initially it was an occasional problem, now it seems permanent. The Asus logo shows up while the machine is starting up so surely that dismisses some of the minor suggestions like cables etc, then some design logo shows briefly and then nothing, then no signal. It’s like the machine goes into some sort of impasse or loop during the start up phase. Then of course you can’t see anything to do anything. We can only turn the machine off to go through that again. It’s Windows 8 by the way (though might as well be Windows 0)

  14. Ilona Stewart

    I also receive multiple requests to sign up to your newsletter. I am using Windows 8.1. Any suggestions?

    Thanks. Ilona Stewart

    • Mark Jacobs

      Unfortunately, those pop-ups are one of the things which help make it possible for Leo to offer such a great service for free. As it says in the linked article, “The newsletter subscription pop-ups are actually vital to Ask Leo!’s survival. I have run without it, and the results were not pretty. It, like some amount of advertising, are what helps pay the bills, and keep Ask Leo! free and vibrant.”
      This article explains why and how to block them if they get too annoying.
      https://newsletter.askleo.com/why-do-i-keep-g-1/

  15. grammars

    My Lenovo Thinkcentre & Ideapad are about the same age; Microsoft no longer supports them, bulocal fixit guy transplanted W7 & dusted off Ideapad’s wifi to talk to desktop. Several months later, with more use/variety, changes that require me to be the “administrator” & I’m not, probably. I can track down fixit g. but is there a quick way to get round that? The necessary installed M.Office is there, but I can’t open & use bcs computer innards are no longer those from the IMEI ID string that’s clearly printed on the old desktop frame. (I think I may have just used this foreign language to say ‘I have your bassoon” when I wanted to ask “How can I become the administrator?”)

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