UEFI boot (Unified Extensible Firmware Interface) Guide

UEFI, or Unified Extensible Firmware Interface, is the modern replacement for BIOS. It improves security, boot speed, and hardware compatibility on most newer systems. This guide explains what UEFI is, how it works, and how to manage UEFI settings for better control over your PC.

🧠 What Is UEFI?

UEFI is the standard firmware interface on most modern computers. It replaced the legacy BIOS system and offers key advantages:

⚡ Faster startup times
🔒 Secure Boot protection against malware
💽 Support for large drives (2TB+ via GPT)
🖱️ A graphical interface with mouse support
🧰 Advanced diagnostics and system control

🆚 UEFI vs BIOS: What’s the Difference?

BIOS (Legacy)

Uses MBR partitioning
Limited to 2TB drives
Text-only interface, keyboard only
16-bit code limits advanced features

UEFI (Modern)

Uses GPT partitioning
Supports disks larger than 2TB
GUI with mouse and keyboard
32- or 64-bit code supports richer features

🔍 How to Check if Your System Uses UEFI or BIOS

Option 1 – System Information

Press Win + R, type msinfo32, and press Enter.
Find BIOS Mode:
- If it says UEFI, you’re using UEFI.
- If it says Legacy, your system uses BIOS.

Option 2 – Command Prompt

Open Command Prompt (Admin)
Type:

bcdedit /enum

If you see \EFI\Microsoft\Boot\bootmgfw.efi, it’s UEFI.

🧭 UEFI Boot Process (Simplified)

UEFI firmware powers on the hardware
The UEFI boot process begins when the firmware powers on your system hardware. It then reads boot information from the EFI System Partition (ESP)
Loads the Boot Manager (e.g., Windows Boot Manager or GRUB)
Bootloader starts the operating system

🔒 What Is Secure Boot?

Secure Boot is a UEFI feature that blocks unsigned or untrusted boot software.

To check Secure Boot status:

Run msinfo32 and look for Secure Boot State:
- On = enabled
- Off = disabled

To enable Secure Boot:

Restart and enter UEFI settings (usually F2, DEL, ESC, or F12)
Find the Secure Boot section
Enable it and save changes

🔑 How to Access UEFI Firmware Settings

Go to Settings > Update & Security > Recovery
Under Advanced startup, click Restart now
Navigate to Troubleshoot > Advanced options > UEFI Firmware Settings
Click Restart to enter the UEFI menu

You can also press your motherboard’s key during boot (usually F2, DEL, ESC, or F12).

💾 What Is the EFI System Partition (ESP)?

The ESP is a special partition where UEFI stores boot files.

To check for ESP:

Open Command Prompt (Admin)
Run these commands:

diskpart
list disk
select disk 0
list partition

Look for EFI System Partition in the list.

🔄 How to Convert MBR to GPT for UEFI Boot Compatibility

Without data loss (Windows 10 or newer):

mbr2gpt /convert /allowFullOS

Then restart your PC.

With data loss (manual conversion):

Backup your data
Open Disk Management
Delete all partitions
Right-click the disk > Convert to GPT
Create new partitions and format the drive

🛠 How to Fix UEFI Boot Problems

Option 1 – Rebuild Boot Configuration Data (BCD):

Boot into Windows Recovery
Open Command Prompt and run:

bootrec /fixmbr
bootrec /fixboot
bootrec /scanos
bootrec /rebuildbcd

Restart afterward.

Option 2 – Restore the EFI Partition:

diskpart
list disk
select disk 0
list partition
select partition X   # (Replace X with ESP number)
assign letter=S
exit
bcdboot C:\Windows /s S: /f UEFI

Then restart your system.

✅ Benefits of Using UEFI

🚀 Faster and more efficient booting
🔐 Enhanced security with Secure Boot
💽 Support for modern, high-capacity drives
🧰 Access to diagnostics and recovery tools
🖱️ Graphical configuration and navigation

UEFI is the future of system firmware, offering both flexibility and robust protection for modern computing environments. Understanding how UEFI boot works allows users to troubleshoot startup issues and configure modern systems for better speed and security. Further detail on this topic can be found on Leviathan Security. If you’re looking to make more tweaks to Windows 10 in regards to anonymity please check out our guide on the topic.