How to Boot From a USB Device

Make your PC boot from a USB flash drive or external hard drive

What to Know

  • Change the BIOS boot order, connect the USB drive, and restart the computer. The USB boot process usually starts immediately.
  • If it does not, recheck the BIOS boot order, remove other devices, copy the files again, try another port, or update the motherboard BIOS.
  • If your computer was manufactured around 2001 or before, it might not have the ability to boot from a USB drive.

When you boot from a USB device, you're running your computer with the operating system installed on the USB device. When you start your computer normally, you're running it with the operating system installed on your internal hard drive—such as Windows, Linux, or macOS.

How to Boot From a USB Device

Follow these steps to boot from a flash drive, an external hard drive, or some other bootable USB device. It should take anywhere from 10 to 20 minutes, depending on if you have to make changes to how your computer starts up.

These instructions assume you already have a bootable flash drive ready to go, but if not, we have a guide on how to create a bootable USB flash drive of OS X Mavericks Installer and a how-to for creating a Windows 11 bootable USB drive.

  1. Change the boot order in BIOS so the USB device option is listed first. The BIOS is rarely set up this way by default.

    Removable Devices listed first in the boot order of PhoenixBIOS Setup Utility

    If the USB boot option is not first in the boot sequence, your PC will start "normally" (i.e., boot from your hard drive) without even looking at any boot information that might be on your USB device.

    The BIOS on most computers lists the USB boot option as USB or Removable Devices, but some confusingly list it as a Hard Drive option, so be sure to dig around if you're having trouble finding the right one to choose.

    After setting your USB device as the first boot device, your computer will check it for boot information each time your computer starts. Leaving your computer configured this way shouldn't cause problems unless you plan on leaving the bootable USB device attached all the time.

  2. Attach the USB device to your computer via any available USB port.

    USB device plugged into laptop
    pbombaert / Moment / Getty Images

    Creating a bootable flash drive or configuring an external hard drive as bootable is a task in itself. Chances are you made it to these instructions here because you know whatever USB device you have should be bootable after properly configuring BIOS.

  3. Restart your computer.

    Since you're not actually inside of the operating system at this point, restarting isn't the same as using normal restart buttons. Instead, BIOS should explain which key to press—such as F10—to save the boot order changes and restart the computer.

  4. Watch for a Press any key to boot from external device... message.

    Press any key to boot from external device prompt

    You may be prompted with a message to press a key on some bootable devices before the computer boots from the flash drive or another USB device.

    If this happens, and you do nothing, your computer will check for boot information on the next boot device in the list in BIOS (see Step 1), which will probably be your hard drive.

    Most of the time, when trying to boot from a USB device, there is no key-press prompt. The USB boot process usually starts immediately.

  5. Your computer should now boot from the flash drive or USB based external hard drive.

    What happens now depends on what the bootable USB device was intended for. If you're booting from Windows 11, Windows 10, etc. installation files on a flash drive, the operating system setup will begin. If you're booting from a DBAN flash drive you created, it will start. You get the idea.

What to Do When the USB Device Won't Boot

If you tried the above steps, but your computer didn't boot from the USB device, check out some of the tips below. There are several places that this process can get hung up at.

  1. Recheck the boot order in BIOS (Step 1). The number one reason a bootable flash drive or another USB device won't boot is that BIOS isn't configured to check the USB port first.

  2. Didn't find a "USB Device" boot order listing in BIOS? If your computer was manufactured around 2001 or before, it might not have this ability.

    If your computer is newer, check for some other ways that the USB option might be worded. In some BIOS versions, it's called "Removable Devices" or "External Devices."

  3. Remove other USB devices. Other connected USB devices, like printers, external media card readers, etc., could be consuming too much power or causing some other problem, preventing the computer from booting from a flash drive or another device. Unplug all other USB devices and try again.

    Or, if you have multiple bootable devices plugged in at once, the computer might simply be booting to the wrong device, in which case the easiest fix would be to remove all USB storage devices but the one you want to use right now.

  4. Copy the files to the USB device again. If you created the bootable flash drive or external hard drive yourself, which you probably did, repeat whatever steps you took again. You may have made a mistake during the process.

    If you started with an ISO image, burn the ISO file to a USB. Getting an ISO file onto a USB drive, like a flash drive, isn't as easy as just expanding or copying the file there.

  5. Switch to another USB port. The BIOS on some motherboards only checks the first few USB ports. Switch to another USB port and restart your computer.

  6. Update your motherboard's BIOS. If your computer is ancient, the BIOS version running on the motherboard may not support booting directly from a USB device. Try updating the BIOS and checking again for this feature.

  • What is BIOS on a computer?

    BIOS stands for Basic Input/Output System. It's the built-in core processor software responsible for booting up your computer.

  • How do you boot your Mac from a USB?

    Insert the USB device into an open slot. Turn on or restart your Mac, then press and hold the Option key to open Startup Manager. Find and select the USB you wish to boot from.

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