Sleep mode (ACPI S3) cuts power to most hardware, including the network interface. The only exceptions are special low-power states like Modern Standby (S0 Low Power Idle) on newer Windows/Intel devices, but that’s designed for quick resume, not active downloads.

It is one of the most common frustrations for computer users. Here is the short answer, the long explanation, and how to make sure your downloads finish while you aren't at your desk.

However, you can easily change your settings to keep downloads running while the screen is off or the lid is closed.

Windows computers are designed to disconnect from the network when entering sleep to conserve power. To keep downloads active, you must prevent the system from sleeping.