Can you turn on a computer that is off? Honestly, mostly not
This is the question people ask after their first "the machine is asleep" failure, and the honest answer is more limited than the internet suggests. Wake-on-LAN is real, but almost every guide skips the conditions that make it fail.
What Wake-on-LAN actually is
The network card keeps a trickle of power when the machine is off, and listens for a specially formed broadcast — the "magic packet" — containing its MAC address repeated sixteen times. On receiving it, the card signals the motherboard to power on. That is the whole mechanism.
It requires four things at once, and all four are commonly missing:
- BIOS/UEFI support, enabled. Usually "Wake on LAN", "Power on by PCI-E" or similar. Frequently off by default.
- The network adapter configured to allow it. Device Manager → adapter → Power Management → "Allow this device to wake the computer", plus "Only allow a magic packet".
- Fast startup disabled on Windows. Fast startup puts the machine into a hybrid state that often does not respond to WoL. This is the single most common reason a correctly configured setup does nothing.
- A wired connection. Wake-on-Wireless exists and is unreliable on most consumer hardware. Treat WoL as an Ethernet feature.
Why it usually does not work over the internet
The magic packet is a broadcast to the local subnet. Broadcasts do not route — your ISP will not carry one to your home network, and there is nothing to forward it to because the target machine is off and therefore has no IP address for the router to send it to.
The workarounds all involve something else on the network that is already awake:
- A router that can send WoL itself. Many can, either natively or with OpenWrt. You log into the router from outside and tell it to wake the machine. This is the cleanest approach when the router supports it.
- A second always-on device. A Raspberry Pi, a NAS, or any small box that stays awake and can be reached, which then sends the packet on the local network. This is what most people who need this actually run.
- Directed broadcast forwarding. Some routers can forward a packet to the subnet broadcast address, with a static ARP entry for the sleeping machine. It works, it is fiddly, and it is disabled by default on most gear for good reasons.
The alternative nobody mentions: do not let it turn off
A modern desktop idling with the screen off draws very little — commonly 15 to 40 watts, which at typical rates is a small handful of currency units a month. Against the cost of being locked out of a machine you needed, that is usually not a close call.
The disciplined version is to keep the machine awake but let the display sleep, disable hibernation, and set the BIOS to power on after AC loss so a power cut does not strand you. That combination covers the realistic failure modes without any of the WoL configuration surface — see preparing a PC that has to stay reachable.
If the machine is a laptop
Laptops make all of this worse. Lid-closed suspend overrides most settings, battery-saving profiles are aggressive, and Wake-on-Wireless is unreliable. If a laptop must be reachable while unattended, keep it plugged in, lid open, sleep disabled — or accept that you will not reach it and plan accordingly.
What to check first when a wake attempt does nothing
| Symptom | Check |
|---|---|
| Nothing happens at all, even from the same LAN | Fast startup still enabled, or BIOS WoL off |
| Works from the same LAN, not from outside | Expected — broadcasts do not route; you need a router or a helper device |
| Worked once, then stopped | A Windows update re-enabled fast startup, which happens |
| Works from sleep but not from full shutdown | BIOS setting covers S3 only; look for a separate "power on by PCI-E" option |
| Wi-Fi only machine | Treat as unsupported and use a wired link or leave it awake |
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