What does UEFI stand for?
UEFI stands for Unified Extensible Firmware Interface. The modern firmware that replaced BIOS, with a graphical setup, support for drives larger than 2 TB through GPT partitioning, and Secure Boot, which refuses to load unsigned boot code. UEFI boots from GPT disks; legacy BIOS mode boots from MBR.
UEFI is the firmware interface that starts a modern PC and hands control to the operating system. It replaced the legacy BIOS. It can boot from GPT disks, so the boot drive is not limited to 2 TB, it loads boot files from a dedicated EFI system partition, and it supports Secure Boot, which checks the signature of boot software before running it. Most firmware setup screens still say BIOS on the key prompt, but the firmware underneath is UEFI.
UEFI in practice: an example
A technician clones an old installation to a new 4 TB drive and the PC refuses to boot from it. The old disk used MBR with the firmware in legacy mode. After converting the disk to GPT and switching the firmware to UEFI mode, the system starts and the whole 4 TB is usable.
What UEFI is confused with
UEFI vs BIOS: what is the difference?
The legacy BIOS is the older 16-bit firmware that boots from MBR disks. UEFI is its replacement, with GPT support, Secure Boot and a richer setup interface. What BIOS stands for
UEFI vs Secure Boot: what is the difference?
Secure Boot is one feature of UEFI, not another name for it. A PC can run UEFI firmware with Secure Boot turned off.
Which exams cover UEFI?
UEFI is on the official CompTIA acronym list for one of the four exams covered here.
- A+ 220-1201 and 220-1202: 220-1201 3.0 (Hardware); 220-1202 1.0 (Operating Systems); 220-1202 2.0 (Security).
Each number is a CompTIA exam objective and the name in brackets is its domain. The exam puts the term in a scenario; it does not ask you to recite the expansion.
Check yourself: two practice questions
Written by CertSprint for this page. They are not taken from any exam.
1. A technician must enable Secure Boot before installing Windows 11. Which firmware mode is required?
- Legacy BIOS with an MBR disk
- UEFI
- PXE only
- Safe Mode
Show the answer
B. UEFI. Secure Boot is a UEFI feature and does not exist in legacy BIOS mode. PXE is a network boot method and Safe Mode is a Windows start-up option.
2. Which partition style does a disk need so that a PC in UEFI mode can boot Windows from it?
- MBR
- GPT
- FAT16
- Dynamic
Show the answer
B. GPT. Windows boots in UEFI mode from GPT disks and in legacy BIOS mode from MBR disks. FAT16 is a file system and dynamic is a disk type, not a partition style for booting.
Sources: Microsoft Learn: UEFI in Windows; Microsoft Learn: Boot to UEFI mode or legacy BIOS mode; Microsoft Learn: Secure Boot; NIST glossary: Unified Extensible Firmware Interface. The acronym and its expansion come from CompTIA's official acronym lists, linked from each exam glossary above. The explanation, example and questions are CertSprint's own, checked against these sources on 11 November 2026.