UEFI (Unified Extensible Firmware Interface)

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UEFI is the acronym for “Unified Extensible Firmware Interface” that takes the place of BIOS (Basic Input/Output System) on PCs. Its main purpose is to do what BIOS does and improve them with additional features and extend already-existing capabilities. BIOS is the most basic firmware that initiates all the hardware on the system and boots the operating system. Since it was quite a primitive firmware, hardware companies made their way for a more capable firmware standard that provides a wider array of options: UEFI.

The history of UEFI

The “EFI” of UEFI goes back to the mid-90s. Intel-HP Itanium servers were limited by the BIOS capabilities. So, Intel decided to find a solution for this problem and named it Intel Boot Initiative, later renaming it Extensible Firmware Interface (EFI). In 2005, the company stopped the development of EFI specifications and contributed it to the Unified EFI Forum; resulting in the creation of the Unified Extensible Firmware Interface, UEFI.

Like BIOS 2.0

As we mentioned before, UEFI is developed to deliver additional capabilities over BIOS. Those capabilities include the ability to boot from a disk that contains partitions over 2 TB with GPT, 32-bit/64-bit environments, C language programming, modular design, and backward/forward compatibility. Additionally, it enables users to navigate through the most basic settings of the PC in a way more advanced user interface, compared to BIOS, enabling mouse navigation. UEFI can connect to the network as well; the motherboard manufacturers currently utilize this capability for directly delivering the UEFI firmware patches without the need of installing an additional operating system.

UEFI classes

UEFI has several classes depending on its feature set. It starts with Class 0; which means it is basically legacy BIOS. Class 1 is the first UEFI level that works like legacy BIOS with its CSM feature. CSM means Compatibility Support Module which enables UEFI systems simply act like BIOS under the hood. Class 2 delivers CSM as an option; meaning the user can select between legacy BIOS mode and UEFI. Class 3 means it can only work as UEFI; there is no backward compatibility of BIOS for operating systems. The Class 3+ means UEFI delivers Secure Boot as well, which is a requirement for Windows 11 operating system.

Important features of UEFI

The CSM mode is required to boot operating systems which does not support UEFI booting. UEFI booting does not rely on a boot sector on the disk and is meant to utilize GPT partitioning instead of MBR. But still, it can also work with MBR partitioning. Secure Boot, on the other hand, is an important security feature designed to prevent malicious software from loading when the PC boots.


What is the UEFI boot mode?

UEFI boot mode is the standard boot procedure that UEFI firmware is meant to do. It scans the bootable devices for the GPT partition to continue the process.

Should UEFI boot be enabled?

UEFI boot should be enabled since it also allows the Secure Boot feature, which is required by Windows 11.

Can you boot to a USB in UEFI?

Yes, you can boot to a USB device in UEFI.

What is the difference between UEFI and BIOS?

You can think of UEFI as “BIOS 2.0”; UEFI does the same thing as BIOS but delivers way more features to the systems.

What is the difference between EFI and UEFI?

UEFI is the firmware itself while EFI is the file extension for the boot process in UEFI/GPT systems.


UEFI can run both MBR and GPT. However, UEFI is designed to run with GPT; utilizing MBR will disable some UEFI features.

Does Linux support UEFI?

Many of the modern Linux distributions support UEFI firmware.

Is UEFI boot faster than legacy?

Yes, UEFI/GPT boot is faster than legacy boot/MBR.

What is the UEFI PXE boot?

PXE boot is the acronym for Preboot eXecution Environment, which allows booting via other devices in the same network and does not require a storage device in the system itself.

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