Need to start your computer from a USB flash drive instead of the internal hard drive? Whether you are installing Windows, reinstalling macOS, running a recovery environment, or troubleshooting a computer that will not start normally, booting from USB can be extremely useful.
The process is fairly straightforward, but the exact steps depend on whether you are using a Windows PC or a Mac. You may need to open the Boot Menu, change the UEFI/BIOS boot order, or use a specific startup key on a Mac.
Before you begin, make sure your USB drive is actually bootable. Simply copying an ISO file to a flash drive usually is not enough. Once the drive is prepared correctly, you can follow the steps below to boot your computer from it.
Set Your Computer to Boot from a USB Flash Drive [Windows & macOS]
![Set Your Computer to Boot from a USB Flash Drive [Windows & macOS]](https://tech-tips-now.com/wp-content/uploads/2026/08/Set-Your-Computer-to-Boot-from-a-USB-Flash-Drive-Windows-macOS-1-1024x576.jpg)
Below, I’ve mentioned the steps for both Windows and Mac devices; follow them to set your computer to boot from a USB Flash drive:
- To boot a Windows PC from USB, connect the bootable USB flash drive, restart the computer, and repeatedly press the appropriate Boot Menu key, such as F12, F11, Esc, or another manufacturer-specific key.
- Select the USB flash drive from the Boot Menu and press Enter. If the USB drive does not appear, open UEFI/BIOS settings and make sure USB booting is enabled.
- To permanently boot from USB on Windows, open the UEFI/BIOS firmware settings, move the USB device above the internal drive in the boot priority list, save the changes, and restart.
- On an Intel-based Mac, connect the bootable USB drive, shut down the Mac, turn it on, and immediately hold the Option (⌥) key until the available startup disks appear.
- On an Apple silicon Mac, such as a Mac with an M1, M2, M3, M4, or later chip, shut down the Mac, connect the USB drive, press and hold the power button until the startup options appear, and select the available bootable drive.
Step 1: Prepare a Bootable USB Flash Drive
The first thing you need is a bootable USB flash drive. A regular USB drive containing installation files will not necessarily work as a startup device.
For Windows, you can create bootable installation media using Microsoft’s official media creation tools or another trusted utility. For macOS, the process depends on what you are trying to accomplish and which version of macOS you want to use.
Keep in mind that creating bootable media can erase the USB drive. If the flash drive contains important files, back them up before turning it into bootable media.
A USB drive with at least 8 GB of storage is commonly enough for many Windows installation tasks, although newer installation images or specialized recovery environments may require more space.
Step 2: Connect the USB Drive to Your Computer
Once your USB drive is ready, connect it directly to the computer.
If your computer has several USB ports, try a different port if the drive is not detected. On some systems, especially older computers, certain ports may behave differently during startup.
If you are using a USB-C flash drive or an adapter, make sure the connection is secure. For troubleshooting purposes, a direct USB connection is usually preferable to a hub.
Do not remove the flash drive while the computer is starting. Wait until the computer has either booted from it or returned to the normal operating system.
Step 3: Open the Windows Boot Menu
If you are using a Windows PC, you usually do not need to permanently change the boot order. The easier option is to use the temporary Boot Menu.
Restart your computer and begin pressing the appropriate boot-menu key immediately after the computer starts. Depending on the manufacturer, this may be F12, F11, F9, Esc, or another key.
For example, Dell systems commonly use F12, while other manufacturers may use a different key. If you see the manufacturer’s logo when the computer starts, look for a brief message telling you which key opens the boot menu.
Once the Boot Menu appears, use the keyboard to highlight your USB storage device and press Enter.
Step 4: Select the USB Flash Drive
After opening the Boot Menu, you should see several startup options. Your internal SSD or hard drive will normally be listed alongside other available devices.
Look for an entry that identifies your USB flash drive. It may appear under the manufacturer’s name, the drive’s model number, or a description such as UEFI USB Device.
Select the USB option and press Enter.
If everything is configured correctly, the computer should begin loading the software stored on the USB drive instead of starting Windows from the internal drive.
If Windows starts normally, restart the computer and try the Boot Menu again. You may have selected the wrong device or missed the boot-menu key.
Step 5: Change the Windows Boot Order Through UEFI/BIOS
If you want the computer to automatically check the USB drive first, you can change the boot priority.
Restart the computer and enter the UEFI/BIOS firmware settings. The required key varies by manufacturer and may include F2, Delete, Esc, or another key.
Once inside the firmware interface, look for a section named Boot, Boot Order, Boot Priority, or something similar.
Move the USB device above the internal SSD or hard drive. Save your changes and exit the firmware settings.
The computer will restart and attempt to boot from the USB device first.
For most users, however, the temporary Boot Menu is safer because it does not permanently change the computer’s startup order.
Step 6: Check Secure Boot if the USB Will Not Start
Sometimes a perfectly prepared USB drive does not boot because of Secure Boot or compatibility settings.
Secure Boot is a security feature designed to prevent unauthorized software from loading during startup. Some bootable tools and older operating systems may not work while Secure Boot is enabled.
If your USB drive appears in the Boot Menu but refuses to start, check your computer’s UEFI settings for Secure Boot and compatibility options.
Do not disable security features unnecessarily. If the USB drive is designed to support Secure Boot, leave it enabled. Only change firmware settings when you understand why the change is required.
Step 7: Boot from USB on an Intel-Based Mac
The procedure is different on an Intel-based Mac.
First, connect the bootable USB drive and shut down the Mac completely. Turn it on and immediately press and hold the Option (⌥) key.
Continue holding the key until the Mac displays its available startup disks.
You should see the USB drive if it is compatible and properly prepared. Select the USB volume and continue with startup.
If the USB drive does not appear, make sure it was created specifically for the Mac and is compatible with the Mac’s hardware and startup security settings.
Step 8: Boot from USB on an Apple Silicon Mac
Apple Silicon Macs use a different startup process. This includes Macs powered by M-series chips.
Start with the Mac completely shut down. Connect the bootable USB drive, then press and hold the power button.
Keep holding it until you see Loading startup options or the startup options screen.
Available startup disks should appear. Select the appropriate USB drive and continue.
Apple silicon Macs also use additional startup security controls, so not every bootable USB device will automatically be allowed to start. If an external startup disk is blocked, you may need to adjust the Mac’s startup security configuration using macOS Recovery.
Step 9: Confirm That the Computer Actually Booted from USB
After selecting the USB drive, give the computer a little time to load.
You might see a Windows Setup screen, recovery environment, Linux desktop, macOS installer, diagnostic utility, or another interface depending on what you placed on the USB drive.
If you reach the expected interface, the computer successfully booted from USB.
If the normal operating system starts instead, go back and verify that you selected the correct USB device and that the flash drive is genuinely bootable.
Additional Tips
Use a Reliable USB Drive
A failing or very old flash drive can cause unexpected boot problems. If the computer repeatedly fails to recognize the USB, try another USB flash drive.
Use the Temporary Boot Menu When Possible
Changing the permanent boot order is usually unnecessary for a one-time installation or recovery task. Using the Boot Menu lets you select the USB drive for a single startup without changing your normal configuration.
Keep Your Important Files Backed Up
If you are booting from USB because you plan to reinstall an operating system, remember that installation or formatting can potentially erase data. Back up important files before proceeding.
Try Another USB Port
If the drive does not appear, try another port. If you are using an adapter or hub, connect the drive directly whenever possible.
Make Sure the USB Matches Your Computer
A bootable USB created for one operating system or hardware configuration may not work on another computer. Check whether the drive uses the appropriate UEFI, partition, filesystem, and architecture requirements.
FAQs
Why won’t my computer boot from the USB?
The USB may not actually be bootable, the wrong device may have been selected, or your computer’s UEFI/BIOS settings may be preventing it from starting. Try recreating the USB and checking the Boot Menu.
What key opens the Boot Menu in Windows?
There is no universal key. Common choices include F12, F11, F9, Esc, and F8, depending on the computer manufacturer. Watch the startup screen for the correct key or check the manufacturer’s documentation.
Do I need to change the boot order?
Not necessarily. For a one-time USB startup, the temporary Boot Menu is usually the easiest approach. Change the permanent boot order only when you specifically need the computer to prioritize USB devices.
Can I boot a Mac from any USB drive?
No. The USB drive must be properly bootable and compatible with the Mac. Intel-based Macs and Apple silicon Macs also use different startup procedures and security controls.
Why doesn’t my USB appear on my Mac?
The drive may not be correctly prepared, may not contain compatible startup software, or may be blocked by the Mac’s startup security settings. Try another USB port and verify that the drive was created for the appropriate Mac architecture.
Can I return to normal Windows or macOS startup?
Yes. Simply restart the computer without selecting the USB drive. If you changed the permanent boot order, restore the internal SSD or normal startup disk as the primary boot device.