UEFI replaces the older BIOS system that starts your computer

UEFI (Unified Extensible Firmware Interface) is the modern replacement for BIOS — the software that runs before Windows, macOS, or Linux loads. It sits between your hardware and your operating system, handling startup tasks like checking that your hard drive works and deciding which device to boot from. Most computers made after 2010 use UEFI instead of the older BIOS system.

The main difference you will notice: UEFI boots faster, handles larger hard drives without workarounds, and has a graphical menu instead of text-only screens. If you have ever restarted your computer and pressed Delete or F2 to change boot order or turn off Secure Boot, you were inside UEFI.

You do not need to think about UEFI during normal use. It only matters when you are troubleshooting startup problems, installing a new operating system, or changing hardware settings.

Key Takeaways

  • UEFI is the firmware that starts your computer and loads your operating system, replacing the older BIOS standard on most modern machines.
  • UEFI boots faster than BIOS, supports hard drives larger than 2 terabytes without special setup, and shows a graphical menu instead of text screens.
  • You access UEFI by restarting your computer and pressing a key like Delete, F2, or F12 during startup — the exact key appears on your boot screen.
  • Secure Boot, a UEFI feature, prevents unauthorized software from running at startup but can block some operating systems or tools you want to use.

How UEFI starts your computer

When you press the power button, UEFI runs before anything else. It checks that your hardware is working — your RAM, your storage drive, your keyboard. Then it looks for an operating system on your drives in a specific order you can change. Once it finds one, it hands control over to Windows, macOS, or Linux, and those systems take over.

This process takes seconds on modern computers. UEFI is designed to be fast and to get out of the way. You see a logo or a loading bar, and then your operating system appears. If something goes wrong — a drive fails, a cable comes loose, or a file gets corrupted — UEFI will either try the next drive in the boot order or show an error message.

UEFI vs. BIOS: what changed

BIOS is the older firmware standard that computers used from the 1980s until around 2010. It was text-only, slower to boot, and could not handle hard drives larger than about 2 terabytes. UEFI was designed to fix these limits.

The practical differences: UEFI has a graphical menu with a mouse cursor instead of arrow keys and text. UEFI boots in seconds instead of tens of seconds. UEFI supports modern security features like Secure Boot. And UEFI can work with hard drives of any size without special partitioning tricks. Some very old computers still use BIOS, but you are unlikely to encounter one unless you are working with hardware from before 2010.

Secure Boot and what it does

Secure Boot is a UEFI feature that checks whether your operating system is legitimate before running it. When Secure Boot is on, UEFI will only start Windows, macOS, or Linux if they have a digital signature that UEFI recognizes as genuine. This prevents malware from replacing your operating system with a fake one that steals your passwords.

Secure Boot is on by default on most new computers. It works silently in the background and you will never notice it. However, if you are installing an older version of Linux, using a bootable USB tool, or making other changes to how your computer starts, Secure Boot may block you. In those cases, you need to restart, enter UEFI, and turn Secure Boot off temporarily. Once you are done, you should turn it back on.

How to enter UEFI on your computer

Restart your computer and watch the screen carefully during startup. You will see a message like "Press Delete to enter Setup" or "Press F2 for UEFI Settings." The key varies by manufacturer — common ones are Delete, F2, F10, F12, and Esc. Press that key repeatedly as soon as you see the message, before Windows or macOS loads.

If you miss the window, restart again and try the same key. On some computers, especially laptops, you may need to hold the key down instead of tapping it. If nothing happens after several tries, look up your specific computer model — manufacturers sometimes use unusual keys.

Once you are inside UEFI, you will see a menu with options like Boot Order, Secure Boot, and System Information. Use the arrow keys or mouse to navigate. Do not change anything unless you know what you are doing — incorrect settings can prevent your computer from starting. When you are done, look for an option like "Save and Exit" or "Exit Without Saving."

Common UEFI settings you might need to change

Boot Order tells your computer which drive to try first when starting. If you want to boot from a USB drive to install Windows or run a repair tool, you move USB to the top of the list. After you are done, move your main hard drive back to the top so your computer starts normally.

Secure Boot blocks unsigned operating systems from running. Turn it off if you are installing Linux or using specialized tools, then turn it back on when you are finished. Fast Boot skips some hardware checks to save a few seconds during startup — it is safe to leave on. Legacy Boot is an old mode for very old operating systems; leave it off unless you have a specific reason to use it.

Most other settings should be left alone. If you change something and your computer will not start, restart and enter UEFI again, then look for a "Reset to Defaults" or "Load Defaults" option to undo your changes.

When you might need to know about UEFI

You will encounter UEFI when installing a new operating system, especially Linux. You will need it if your computer will not start and you want to check the boot order or try booting from a repair USB. You will need it if you are adding a new hard drive and want to make sure it is recognized. You will need it if you are troubleshooting why Secure Boot is blocking something you want to run.

In all other situations, UEFI works invisibly. You do not need to think about it, adjust it, or worry about it. It is there to make your computer start reliably and securely, and then get out of the way.

Frequently Asked Questions

Can I switch my computer from UEFI back to BIOS?

Some computers have a Legacy Boot mode that lets you use BIOS instead of UEFI, but most modern computers do not. Even if your computer supports it, there is no reason to switch — UEFI is faster and more secure. If you are trying to run old software that requires BIOS, the better solution is to use a virtual machine or find a newer version of the software.

What happens if I turn off Secure Boot?

Your computer will start unsigned operating systems and tools. This is necessary for some Linux distributions and specialized repair utilities, but it removes a layer of protection against malware that replaces your operating system. Turn Secure Boot back on as soon as you are done with what you needed to do.

Why does my computer take a long time to start even though UEFI is supposed to be fast?

UEFI itself is fast, but your operating system, background programs, and hard drive speed also matter. If startup is slow, the problem is usually Windows or macOS loading programs in the background, not UEFI. Check your Task Manager or Activity Monitor to see what is running at startup.

Is UEFI the same as BIOS?

No. UEFI is the modern replacement for BIOS. They do the same job — starting your computer — but UEFI is faster, more secure, and handles modern hardware better. Most computers made after 2010 use UEFI.

Do I need to do anything to maintain UEFI?

No. UEFI is firmware built into your computer's motherboard and does not need updates or maintenance. It will work the same way for the life of your computer unless you deliberately change its settings.