Computer won't turn on, or the screen stays black? Checks to try in order

You press the power button and nothing happens. Or the computer seems to come on (lights, fan noise) but the screen stays black. Most of the time it's something simple: a loose cable, a drained battery, a monitor on the wrong setting, or a computer that's stuck and needs a full power-off. Work through these steps in order. They're free, and none of them delete your files.

Computer starts but is just slow or freezes once it's running? See Slow or frozen computer.

First: which is it?

• Completely dead: no lights, no fan, no sound → start with Check the power.
• Lights or fan come on, but the screen stays black → go to Lights on, black screen.
• Something shows on screen (an error, a logo that never finishes, a question mark on a Mac) → the computer is on but not starting up all the way. See Starts, but won't finish starting up.

Step-by-step

1. Check the power

   • Make sure the outlet works: plug in a lamp or phone charger to test it. If you use a power strip, make sure it's switched on, or plug straight into the wall.
   • Check that the power cable is undamaged and pushed in firmly at both ends. If you have another compatible cable or charger, try it.
   • Laptops: plug in the charger and wait a while before trying again; a fully drained battery may need time. Make sure you're using the laptop's own charger in its charging port. If the laptop won't charge at all, see Laptop won't charge.

2. Unplug accessories

   A faulty accessory or cable can stop a computer from starting. Unplug everything you don't need: printers, USB drives, external hard drives, USB hubs, docks and phones. Leave only the power (and, on a desktop, the monitor, keyboard and mouse). Then try again.

3. Force it fully off, then turn it on

   Sometimes a computer is stuck in a frozen or sleeping state that looks like it's off.

   • Windows PC: press and hold the power button for about 20 seconds, as Microsoft suggests, then let go, wait a moment, and press it once normally.
   • Mac: press and hold the power button for about 10 seconds, then press and release it normally. On a Mac laptop with Touch ID, the Touch ID button is the power button; press it down, don't just touch it.

   Holding the power button turns the computer off without saving, so only do this when it isn't responding.

4. Desktops: check the monitor

   If the computer's lights and fan come on, the problem may be the screen, not the computer.

   • Make sure the monitor is plugged in and turned on (it usually has its own power light).
   • Check the video cable (HDMI, DisplayPort or VGA) is firmly connected at both ends. If you can, try a different cable or monitor.
   • Laptop connected to an external monitor? Unplug the external monitor and see if the laptop's own screen works.

5. Lights on, black screen: wake the display (Windows)

   Microsoft suggests these keyboard shortcuts when Windows is running but the screen is blank:

   • Press Windows + Ctrl + Shift + B. This restarts the display driver. A beep or a flicker means it worked.
   • Press Windows + P to switch display modes (for example, PC screen only or Duplicate). Press P again to move through the choices and Enter to pick one. This helps if the picture is being sent to a screen that isn't there.
   • Press Ctrl + Alt + Del. If the security screen appears, open Task Manager and restart Windows Explorer (Microsoft's page has the steps).

   Mac: Apple says a blank black, gray or blue screen can appear briefly during a normal startup. If it stays blank, hold the power button for up to 10 seconds to turn it off, then turn it on again.

6. Starts, but won't finish starting up

   • Windows: if Windows shows a blue screen saying “Your device ran into a problem and needs to restart,” or keeps restarting, Microsoft has separate steps for that; see Microsoft: Troubleshooting Windows unexpected restarts and stop code errors. If a black screen started right after an update, the recovery options below may help.
   • Mac: if you see a flashing question mark, a circle with a line through it, or another symbol, your Mac is on but isn't starting up all the way. Apple's steps start from macOS Recovery, which lets you check the startup disk with Disk Utility. See the Apple links in Sources, or ask someone you trust to help.

7. Older Intel-based Mac? Reset the SMC

   Apple says resetting the SMC (the chip that manages power) can help an older, Intel-based Mac that won't turn on. You don't need to do this on a Mac with Apple silicon (M1 or later). The steps depend on the model, so follow Apple's SMC reset guide.

For the confident: Windows recovery options

If Windows still shows only a black screen, turn the computer on and, while it's starting, press and hold the power button for 10 seconds to turn it off. Repeat this 2–3 times until Windows opens the recovery screen. From there, Troubleshoot → Advanced options offers Startup Settings (for Safe Mode) and System Restore, which takes the PC back to a restore point from before the problem started.

Still won't start?

If none of this works, the computer may need repair: for example a failed charger, battery, power supply, screen or drive. Contact the computer's maker (many have free diagnostic tools and phone support) or a repair shop you trust. If your files matter, say so up front; a dead computer doesn't always mean lost files.

Sources

• Microsoft: Troubleshooting blank screens in Windows
• Microsoft: Troubleshooting Windows unexpected restarts and stop code errors
• Apple: If your Mac doesn't turn on
• Apple: If your Mac starts up to a blank screen
• Apple: If your Mac starts up to a question mark
• Apple: How to start up from macOS Recovery
• Apple: How to reset the SMC of your Mac