The cable is plugged in. The projector is on. The screen says "No signal".
It is one of the most common problems before a service, and it is often solved in a few seconds, because the laptop is not sending anything yet. This guide goes through the checks in the order that finds the cause fastest, using Microsoft Support's documentation for Windows, and Renewed Vision's for Mac. Where a tip comes from outside the vendors, it is marked.
Check 1: tell Windows to send the picture
Microsoft's guide to projecting a screen says to press the Windows key and P. It shows four options:
| Option | What it does |
|---|---|
| PC screen only | Uses the laptop screen only. Nothing goes to the projector. |
| Duplicate | Shows the same picture on both screens. |
| Extend | Uses the projector as a second desktop. |
| Second screen only | Shows the picture on the projector only. |
If the laptop is set to PC screen only, the projector has no signal. A university AV support page lists this as the typical reason for a "No HDMI signal" message. Choose Duplicate or Extend and the projector should wake up.
Check 2: make Windows look for the display
If the option is right and the projector is still blank, open Settings, then System, then Display. In the Multiple displays section, press Detect if the screen is not listed. Press Identify to put a number on each screen, so you know which is which.
Microsoft's troubleshooting steps for external monitors also say to confirm the connection itself: check the cable at both ends, check that the display has power, and check that the projector or TV is set to the input you are using, such as HDMI 1 or HDMI 2.
Check 3: the physical path
Cables and adapters fail more often than software. A few points from Microsoft's guidance:
- A single video port supports one external display. To connect more than one, you need a dock or an adapter that supports it.
- A display splitter only duplicates. It cannot extend.
- Try a different cable or port, and try a different display, to see whether the problem follows the cable or the computer.
Third-party how-to guides add some further advice that is useful but not official: an old projector may not accept a high resolution, so try lowering the laptop's resolution, for example to 1080p or 720p at 60 Hz. Some laptops also need a function key, often with a screen icon, to enable the external output, and HDCP-protected content can be blocked on some displays.
Check 4: the picture flickers or drops out
Microsoft Q&A answers explain that the Duplicate mode forces both screens to use a common resolution and timing, which can cause flicker or loss of signal when the two screens do not agree. Using Extend avoids that, or you can set both to a common resolution.
Which mode to choose in a service
Windows plus P gives you three modes that send a picture, and they suit different jobs.
- Duplicate shows the same picture on both screens. It is the simplest, and it is what many people expect. The cost, from Microsoft Q&A answers, is that both screens must agree on a resolution and timing, which can cause flicker with older projectors.
- Extend gives the projector its own desktop. It is what PowerPoint's Presenter View and ProPresenter's separate Audience and Stage screens rely on. PowerPoint switches to it by itself when a slide show starts.
- Second screen only turns the laptop screen off and sends everything to the projector. It is useful when the laptop is closed or when you want to remove distractions, but it makes troubleshooting harder, since you may be working on a screen you cannot see.
If the aim is to get a picture quickly, start with Duplicate. If you are going to use presenter notes, move to Extend once you know the cable works.
Cables, adapters and ports in more detail
When the software settings are right and there is still no picture, the cause is usually physical. Microsoft's point that one video port supports one external display is easy to forget with modern laptops that have a single USB-C port and a dock. Several outputs on the dock do not mean several independent displays; they depend on what the dock and the computer support.
Adapters add another place to fail. An HDMI to VGA converter, for example, needs to be the type that converts a digital signal into an analog one, and a simple passive cable will not do it. If you use an adapter regularly, test it with the same laptop and the same projector, and keep it with the projector, so it does not wander.
On a Mac
Renewed Vision's instructions for ProPresenter say to open the display settings in System Settings and use an extended display instead of mirroring, unless you want mirroring. Renewed Vision also says that NDI and SDI outputs will not appear in the Displays list on a Mac. If you use ProPresenter, restart it after changing displays.
When the computer sees the screen but the software does not
Sometimes the projector works, but your presentation program sends the picture to the wrong place. That is a different problem with a different fix:
- For ProPresenter, see audience screen black or on the wrong monitor.
- For PowerPoint, see Presenter View on the wrong screen.
The checklist
- Is the projector on, and set to the right input?
- Is the cable fully plugged in at both ends?
- Press Windows and P. Is it on Duplicate or Extend, not PC screen only?
- In Display settings, did you press Detect and Identify?
- Does another cable, port or adapter work?
- For an old projector, try a lower resolution at 60 Hz.
- Does the picture flicker in Duplicate? Try Extend.
- On a Mac, is the display extended or mirrored as you intend?
Keep a spare
The cable and adapter checks in step 5 are only useful if you have something to swap. Keep a spare HDMI cable and the right adapter with the equipment, and label them so nobody takes them home. Our Sunday tech preflight checklist lists the other items worth keeping to hand.
How Planify can help
A projector problem is fixed fastest by someone who has done it before.
- A position for the projection operator, with a coordinator and a minimum and maximum number of people.
- Confirmation by tap. Volunteers confirm or decline on WhatsApp.
- Cover from the same position. If someone declines, Planify can ask colleagues who cover that position.
- Share links. Share the schedule so that the media team knows who is on and when.
Which features you get depends on your plan.
Read next: media team scheduling: why sound, cameras and slides can't be swapped.
FAQ
Why does my projector say no signal when the laptop is connected?
Often the laptop is set to PC screen only. Press the Windows key and P and choose Duplicate or Extend. Then check the cable and the projector input.
What does Windows plus P do?
It opens the projection menu with four options: PC screen only, Duplicate, Extend and Second screen only.
Can I connect two projectors to one HDMI port?
Microsoft says a single video port supports one external display. You need a dock or an adapter that supports more than one. A splitter only duplicates the picture.
Why does the picture flicker in Duplicate mode?
Duplicate forces a common resolution and timing on both screens. Extend, or a common resolution, avoids this.
Does a Mac need different settings?
Use an extended display in System Settings, unless you want mirroring. Restart ProPresenter after changing displays.