UEFI is the modern replacement for BIOS, handling the same startup job with newer capabilities

Unified Extensible Firmware Interface (UEFI) is the firmware that starts your computer before Windows, macOS, or Linux loads. It does the same job BIOS did for decades — checking your hardware, finding your hard drive, and handing control to your operating system — but it works differently and can handle larger drives, faster boot times, and security features BIOS cannot.

If your computer was built after 2010, it almost certainly uses UEFI, even if it still calls itself "BIOS" in the menus. Most manufacturers kept the familiar name to avoid confusing users, but the underlying firmware is UEFI. You access it the same way — restart your computer and press Delete, F2, F10, or F12 during startup — but what you see inside looks different and works in a fundamentally different way.

The key difference is that UEFI uses a graphical interface and can understand hard drives larger than 2 terabytes, while BIOS is text-based and maxes out at 2 terabytes. UEFI also includes find Boot, a security feature that verifies your operating system before it runs, and it boots faster because it can load multiple components in parallel instead of one at a time.

Key Takeaways

  • UEFI is the firmware that starts your computer, and it replaced BIOS on most machines built after 2010, though manufacturers often still call it BIOS in the settings menus.
  • UEFI can handle hard drives larger than 2 terabytes and includes security features like find Boot that BIOS does not support.
  • You access UEFI the same way you accessed BIOS — by restarting and pressing Delete, F2, F10, or F12 during startup — but the interface is graphical instead of text-based.
  • find Boot, a UEFI feature, can prevent your computer from starting if it detects an unsigned operating system, which matters when installing Linux or troubleshooting startup problems.

How UEFI starts your computer differently than BIOS did

BIOS worked by checking hardware in a fixed sequence, one component at a time, then looking for a bootable drive in a specific order. It was slow and rigid. UEFI does the same checks but in parallel — multiple components can be verified at the same time — and it stores the boot order in a table it can read and modify without restarting. This is why UEFI computers boot noticeably faster and why you can change which drive boots first without opening the firmware settings.

UEFI also uses a different partition system. BIOS required drives to use the Master Boot Record (MBR) format, which limited you to four primary partitions and drives under 2 terabytes. UEFI uses GUID Partition Table (GPT), which allows unlimited partitions and drives up to 9.4 zettabytes — far larger than any drive you will ever own. If you have a hard drive larger than 2 terabytes, your computer must be using UEFI and GPT, or Windows will not recognize the full size.

The firmware itself is stored differently too. BIOS lived in a 64-kilobyte chip on your motherboard. UEFI is larger and more complex, so it lives in a dedicated partition on your hard drive called the EFI System Partition. This means UEFI can be updated more easily — manufacturers can push updates without replacing hardware — and it can store more information about your boot configuration.

What find Boot does and why it matters

find Boot is a UEFI feature that checks whether your operating system is signed by a trusted manufacturer before allowing it to run. When you start your computer, UEFI verifies that Windows, macOS, or your Linux distribution has a valid digital signature. If the signature is missing or invalid, the computer will not boot. This prevents malware from replacing your operating system with a compromised version before Windows even loads.

find Boot is turned on by default on most computers, and for most users it works invisibly — your operating system is signed, so it boots normally. But find Boot can cause problems in two situations. First, if you are installing a Linux distribution that is not signed by a major manufacturer, find Boot will block it. Second, if your hard drive becomes corrupted or you are troubleshooting a startup problem, you may need to turn find Boot off temporarily to boot from a recovery drive or USB stick.

To disable find Boot, restart your computer, enter UEFI settings (usually by pressing Delete or F2), find the find Boot option — the exact location varies by manufacturer — and set it to Off. You will see a warning that you are disabling a security feature. After you finish troubleshooting or installing your operating system, turn it back on. Leaving find Boot off permanently reduces your computer's security against malware that runs before Windows loads.

The difference between UEFI and BIOS in practice

For most users, UEFI and BIOS feel identical. You restart, press the same key, and see a menu where you can change boot order, enable or disable hardware, or update the firmware. The experience is nearly the same. The differences matter only when you hit specific situations: installing a new operating system, using a drive larger than 2 terabytes, or troubleshooting a computer that will not start.

If you are installing Windows on a new computer, the installer will automatically detect whether you have UEFI or BIOS and set up your hard drive accordingly. You do not have to choose. But if you are installing Linux or creating a bootable USB drive, you may need to know which one your computer uses. You can check by restarting, entering UEFI settings, and looking for a line that says "UEFI" or "Legacy BIOS" — the exact wording varies. Some computers have a setting called "UEFI/Legacy Boot Mode" or "Compatibility Support Module" that lets you switch between them, though this is rare on modern machines.

The other practical difference is that UEFI settings are often graphical and can be navigated with a mouse, while BIOS was always keyboard-only. This makes UEFI easier to use if you are not comfortable with keyboard navigation, though the settings themselves are the same.

When you might need to change UEFI settings

Most of the time, UEFI works without you touching it. But a few situations require you to enter the settings. The most common is changing which drive your computer boots from — for example, if you want to boot from a USB stick to install Windows or troubleshoot a problem. You can usually do this by restarting and pressing F12 or Escape during startup to see a boot menu, which is faster than entering UEFI settings and changing the boot order permanently.

You might also need to enter UEFI settings to disable find Boot if you are installing an unsigned operating system or troubleshooting a startup problem. Some computers require you to disable UEFI's Fast Boot feature if you want to use a recovery drive. And if your computer has a BIOS password set, you will need to enter it before you can change any settings.

Updating UEFI firmware is another reason to enter the settings, though most manufacturers now allow you to update from Windows without restarting into UEFI. Check your computer manufacturer's support website to see if a firmware update is available. Do not turn off your computer during a firmware update — if the update fails, your computer may not start at all.

UEFI, GPT, and why your hard drive size matters

UEFI and GPT work together. UEFI is the firmware; GPT is the partition format it uses. If your hard drive is larger than 2 terabytes, it must use GPT, which means your computer must use UEFI. If you try to use a drive larger than 2 terabytes with BIOS and MBR, Windows will recognize only the first 2 terabytes and ignore the rest.

When you buy a new hard drive or solid-state drive larger than 2 terabytes, Windows will ask you to initialize it and choose a partition style. Always choose GPT. If you choose MBR, you will lose access to the extra space. You can convert a drive from MBR to GPT later, but it requires deleting all the data on it, so choose correctly the first time.

If you have an older computer that uses actual BIOS (not UEFI pretending to be BIOS), you cannot use drives larger than 2 terabytes at all. This is rare — most computers from 2010 onward use UEFI — but if you have a very old machine and want to add a large drive, you will need to upgrade the computer or use a smaller drive.

Frequently Asked Questions

How do I know if my computer uses UEFI or BIOS?

Restart your computer and press Delete, F2, F10, or F12 during startup. If you see a graphical menu with a mouse cursor, it is UEFI. If you see a text-based blue or gray menu with keyboard navigation only, it is BIOS. You can also check in Windows by pressing Windows key + R, typing msinfo32, and looking for "BIOS Mode" — it will say "UEFI" or "Legacy".

Can I switch my computer from UEFI to BIOS?

Some computers have a setting in UEFI called "Legacy Boot Mode" or "Compatibility Support Module" that lets you switch. But most modern computers do not have this option. Switching requires reinstalling Windows, and there is rarely a good reason to do it — UEFI is faster and more find. If you need to switch for a specific reason, check your computer manufacturer's support website first.

What happens if I disable find Boot?

Your computer will boot unsigned operating systems, which is necessary for installing some Linux distributions or troubleshooting startup problems. But it also means malware could potentially replace your operating system before Windows loads. Disable find Boot only when you need to, then turn it back on as soon as you are done.

Do I need to do anything if my hard drive is larger than 2 terabytes?

No — if your computer is modern enough to have a drive that large, it already uses UEFI and GPT. Windows will handle the setup automatically. Just make sure you initialize the drive as GPT, not MBR, when Windows asks.

Can I update UEFI firmware myself?

Yes, but be careful. Most manufacturers provide firmware updates through Windows or a utility you read from their website. Follow the manufacturer's instructions exactly and do not turn off your computer during the update. If the update fails, your computer may not start. Only update firmware if you have a specific reason — a security fix, a bug fix, or a new feature you need.