UEFI vs Legacy - What is the difference?

In this guide, we will learn what are UEFI and Legacy modes and help you understand which mode is better than the other in specific instances. Before diving deep into what UEFI and Legacy Boot modes are and the differences between them, let us discuss how a computer boots and what happens during the boot process. Understanding this will help clear up some concepts. Let us get started.

How a Computer Boots?

When you turn on your computer, it powers on the CPU, the key computer component that processes commands or instructions. At this stage of the boot-up process, there are no instructions loaded into the memory. As such, the CPU switches to the system firmware, which contains instructions for the boot process.

The firmware code performs a Power On Self Test (POST) initialization and sets up all the connected peripherals. Once the POST check is successful, the firmware loads the storage devices and checks for a boot loader. The firmware then switches the instructions to the bootloader to handle the boot process. At this stage, the bootloader, such as LILO and GRUB, takes over, loads the system kernel in the memory, and initializes required processes.

As mentioned, the firmware helps handle hardware initialization during the boot-up process. This firmware is commonly known as BIOS or Basic Input Output System.

What is Legacy Boot?

Legacy Boot refers to the boot process used by the BIOS firmware to initialize hardware devices. The Legacy boot contains a selection of installed devices that get initialized as the computer performs the POST test during the boot process. The legacy boot will check for all connected devices for the Master Boot Record (MBR), usually in the first sector of a disk.

When it can’t find a bootloader in the devices, Legacy switches to the next device in the list and keeps repeating this process until it finds a bootloader, or if not, returns an error.

What is UEFI?

UEFI or Unified Extensible Firmware Interface is a modern way of handling the boot process. UEFI is similar to Legacy, however, it stores the boot data in a .efi file rather than the firmware.

You will often find UEFI boot mode in modern motherboards with very intuitive and user-friendly Interfaces. UEFI boot mode contains a special EFI partition that is used to store the .efi file and is used in the boot process and the bootloader.

Difference between UEFI and Legacy

At a base level, UEFI and Legacy are very similar. However, on a deeper level, they’re also different.

Since UEFI is a BIOS successor, it has better functionalities and features. The differences between UEFI and Legacy are listed in the table below:

UEFI BOOT MODE	LEGACY BOOT MODE
UEFI provides a better User interface.	Legacy Boot mode is traditional and very basic.
It uses the GPT partitioning scheme.	Legacy uses the MBR partition scheme.
UEFI provides faster boot time.	It is slower compared to UEFI.
Since UEFI uses the GPT partitioning scheme, it can support up to 9 zettabytes of storage devices.	The MBR portioning scheme used by Legacy only supports up to 2 TB storage devices.
UEFI runs in 32-bit and 64-bit, allowing support for mouse and touch navigation.	Legacy runs in 16-bit mode that only supports keyboard navigation.
It allows a secure boot that prevents the loading of unauthorized applications. It may also hinder dual boot because it treats operating systems (OS) as applications.	It does not provide a secure boot method, which allows for the loading of unauthorized applications, making dual-booting possible.
It has an easier update process.	It is more complex compared to UEFI.

Although UEFI may sound better than Legacy (and it is), it’s not always the best choice to use, and you may not need it. In some cases, you may have to use Legacy, depending on the features you want. For example, if you want dual booting, UEFI can hinder this process.

Here are other scenarios where you might not need UEFI:

Dual Booting process
When you have less than 2 TB of storage device (stick to MBR)