How to boot from a USB
Learning how to boot from a USB is a useful skill for any PC user. Operating systems and some apps can be run from, and be installed from a USB drive. You do not need to boot to a desktop OS to access apps that can run from the bootloader of a computer. Likewise, if you need to install a new OS or perform a clean install, you will likely use a USB drive to install it.
Getting a system to ignore the installed OS, and boot from a USB isn’t hard if you know what setting needs to be changed and how to access it.
How to Boot from a USB Drive
To boot from a USB, you need to
- Boot to BIOS/UEFI
- Change the first boot device to USB
- Restart the system
The above is a basic rundown of what you need to do to boot from a USB, but we’re going to go into more details because it gets a bit complicated. These directions DO NOT apply to a Mac of any kind.
Before you start: make sure the USB drive is actually bootable
Before touching any firmware settings, confirm that your USB drive has actually been set up as bootable media. Simply copying files onto a flash drive is not enough — the drive needs to be written in a specific way so the system can recognize and start from it.
Here is how to prepare it for the most common use cases:
- Installing Windows: Use Microsoft’s official Media Creation Tool. It handles everything automatically, including the correct partition format for your system.
- Installing Linux or running a rescue tool: Download the ISO file for the OS or tool you want, then use Rufus or BalenaEtcher to write it to the drive. Do not simply copy the ISO file — you must burn it using one of these tools.
Before you begin, run through this quick checklist:
- Drive size: Use at least an 8 GB drive. 16 GB or larger is preferred for Windows.
- Data loss warning: The creation process will erase everything already on the drive, so back up anything important first.
- Match the media to your firmware mode: If your PC uses UEFI (most modern systems do), create GPT/UEFI media when the tool gives you the option. Legacy BIOS systems use MBR-partitioned media.
- FAT32 formatting: Some systems, including certain ASUS motherboards, are pickier about boot media and may only recognize drives formatted as FAT32. Rufus lets you select this manually if needed.
Once you have a properly prepared bootable drive, continue with the steps below.
1. Boot to BIOS/UEFI
In order to boot to BIOS, you need to;
- Turn the system off and turn it on again (or restart if you’re on a desktop OS).
- Tap the F2 or the F10 or the Delete key as the system is starting up to boot to your BIOS/UEFI. If you’re not sure which key to tap, check our post on how to access BIOS.
- You will see a basic windowless menu with tabs. The exact key varies by manufacturer, so consult your motherboard or laptop manual if the common keys don’t work.
Alternative method: enter UEFI from Windows 10 or Windows 11
If your PC boots too quickly for you to catch the startup hotkey — common on systems with Fast Startup enabled or very short splash screens — you can reach UEFI firmware settings directly from within Windows.
On Windows 11:
- Open Settings and go to System > Recovery.
- Under Advanced startup, click Restart now.
- After the PC restarts to the blue menu, select Troubleshoot > Advanced options > UEFI Firmware Settings > Restart.
On Windows 10:
- Open Settings and go to Update & Security > Recovery.
- Under Advanced startup, click Restart now.
- After the PC restarts to the blue menu, select Troubleshoot > Advanced options > UEFI Firmware Settings > Restart.
Your PC will reboot directly into the firmware interface, no hotkey timing required.
2. Check for BIOS/UEFI
You now need to determine if you’re running Legacy BIOS or UEFI. The method for selecting the first boot device will differ based on what firmware interface type you have. Here are reliable ways to find out before or after entering firmware settings.
Method 1 — Check from within Windows (most reliable):
- Press Win + R, type msinfo32, and press Enter.
- In the System Information window, look for the BIOS Mode row near the top.
- It will say either UEFI or Legacy. This is the definitive answer.
Method 2 — Check Disk Management (a useful clue):
- Press Win + R, type diskmgmt.msc, and press Enter.
- Right-click your primary system disk and select Properties, then go to the Volumes tab.
- If the Partition style shows GPT, the system is most likely running UEFI. If it shows MBR, the system is most likely running Legacy BIOS. Treat this as a clue rather than a definitive test, since it is possible (though uncommon) to have a GPT disk on a Legacy system.
A note on Secure Boot: Secure Boot is a UEFI feature, but it can be either enabled or disabled on a UEFI system. Many modern UEFI motherboards also expose CSM (Compatibility Support Module) or Legacy Boot options in the firmware menu. This means you cannot use Secure Boot status alone, or the presence of Legacy options, to determine whether the system is actually running in UEFI or Legacy mode. Use msinfo32 for a definitive answer.
Where to go from here: If msinfo32 shows BIOS Mode: Legacy, follow the BIOS steps in section 3 below. If it shows BIOS Mode: UEFI, skip to section 4.
3. How to Boot from a USB with BIOS
Assuming you’re running the BIOS firmware type, follow these steps to change the boot order for the system.
- Boot to BIOS.
- Go to the Boot tab.
- Look for Boot Order (or similar), and select it by tapping the Enter key.
- Use the arrow keys to select USB disk or USB drive.
- Save the change and exit BIOS.
- Connect the USB drive you want to boot from to your system.
- Turn the system on and it will boot from the USB drive.
4. Change Boot order – UEFI
Changing the boot order in UEFI is slightly different than changing it in BIOS. Because UEFI uses a graphical interface and supports mouse input on many systems, the process can feel more intuitive once you know where to look. There are two ways to do this: a one-time selection that only affects the current startup, or a permanent boot order change.
Option A — One-time boot menu (recommended for most users):
- Connect the USB drive to your system.
- Restart the PC and immediately press the boot menu key as it starts up. This is commonly F12, Esc, F11, or F8 depending on your PC brand — check your motherboard or laptop manual if you are unsure.
- A boot device selection menu will appear. Select your USB drive from the list. It may appear under the drive’s brand name, as “Removable Device,” or as “UEFI: <drive name>”.
- The system will boot from the USB for this startup only. Your normal boot order is not changed.
Option B — Permanent boot order change:
- Enter UEFI setup using the method in section 1 or the Windows alternative method above.
- Navigate to the Boot tab or Boot Option Priorities section.
- Move the USB drive entry — which may appear as “UEFI: <USB name>” or simply as a removable device — to the top of the boot order.
- Save the changes and exit. The PC will now attempt to boot from USB first on every startup.
- After you are done installing or troubleshooting, return to UEFI and move your internal SSD or HDD back to the top of the boot order to prevent the system from looking for a bootable USB on future startups.
Most users only need Option A. Use Option B only if you need to boot from USB repeatedly without pressing a key each time.
Troubleshooting if the PC will not boot from USB
If you followed the steps above and the system still boots to Windows or shows an error, work through this checklist:
- Confirm the USB was created as bootable media. Copying files to a drive is not enough. If you skipped the preparation step, go back and use Media Creation Tool, Rufus, or BalenaEtcher to write the drive correctly.
- Try a different USB port. Some firmware is picky about which port it will boot from. On older systems, a USB 2.0 port (often black rather than blue) is more reliably detected at boot than a USB 3.0 port.
- Unplug other external drives. Having multiple USB storage devices connected can confuse the boot sequence. Disconnect everything except the bootable drive.
- Check how the drive appears in the boot menu. Look for it listed under a brand name, as “Removable Device,” or as “UEFI: <drive name>.” If it does not appear at all, the drive may not be bootable or may not be detected.
- Disable Secure Boot only if your media is unsigned. Some Linux distributions and rescue tools are not signed and will be blocked by Secure Boot. If that is the case, enter UEFI settings and disable Secure Boot. Windows installation media from Microsoft works with Secure Boot on, so do not disable it unless necessary.
- Make sure the media matches your system mode. UEFI systems expect UEFI/GPT boot media, and Legacy BIOS systems expect MBR boot media. A mismatch will result in the drive being unbootable or invisible in the menu. Recreate the drive in the correct format using Rufus.
- Enable USB boot in firmware if the option exists. Some firmware settings have a dedicated toggle for booting from external or USB devices. Check under the Boot tab or an Advanced tab and make sure it is enabled.
- Watch for a “Press any key to boot from USB” prompt. Some systems display this message briefly at startup. If you miss it, the system falls back to the internal drive. Restart and press a key as soon as the prompt appears.
- Restore your boot order when you are finished. After installation or troubleshooting is complete, return to your firmware settings and make sure the internal SSD or HDD is first in the boot order so the system starts normally on its own.
Conclusion
Knowing how to boot from a USB gives you greater control over your system, whether you’re installing a fresh operating system, running a live environment, or troubleshooting a broken Windows installation. UEFI isn’t as common as BIOS, yet. Most people don’t know which they’re running and expect UEFI to act exactly the same as BIOS, which is why it’s sometimes difficult to change the first boot device.
With UEFI, the boot device is set to the HDD or SSD unless it is changed on startup, whereas on BIOS it follows an order of devices regardless of whether all of them are available or not. For a deeper understanding of the differences between BIOS and UEFI firmware, Microsoft’s official documentation on UEFI and Legacy BIOS boot modes is an excellent reference.
