How can I tell if my system was booted as EFI/UEFI or BIOS?


There are two BIOS mode: Legacy BIOS mode and UEFI BIOS mode. In most cases, we don't need to know which BIOS mode our Windows OS is using. But sometimes, we need to know which BIOS mode Windows OS is using. This tutorial will show you how to check if Windows is booted in UEFI or Legacy BIOS mode.

How to Check if Windows is Booted in UEFI or Legacy BIOS Mode?

Method 1: Check if UEFI or Legacy BIOS Mode in System Information in Windows 8 and 10

Press the Windows + R keys to open the Windows Run dialog, type msinfo32.exe, and then press Enter to open System Infomation window. In the right pane of System Summary, you should see the BIOS MODE line. If the value of BIOS MODE is Legacy, then Windows is booted in legacy BIOS mode. If the value of BIOS MODE is UEFI, then Windows is booted in UEFI BIOS mode. Please see the screenshots below.

Method 2: Check if UEFI or Legacy BIOS Mode in setupact.log in Windows 7, 8,...

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I am looking for a way to reliably detect when I boot into WinPE 4 (powershell) (or WinPE 3 (vbs) as an alternative), have I booted from a UEFI or BIOS System? (without running a third party exe as I am in a restricted environment)

This significantly changes how I would be partitioning a windows deployment as the partitions layout changes and format. (GPT vs. MBR, etc)

I have one working that is an adaptation of this C++ code in powershell v3 but it feels pretty hack-ish :

## Check if we can get a dummy flag from the UEFI via the Kernel ## [Bool] check the result of the kernel's fetch of the dummy GUID from UEFI ## The only way I found to do it was using the C++ compiler in powershell Function Compile-UEFIDectectionClass{ $win32UEFICode= @' using System; using System.Runtime.InteropServices; public class UEFI { [DllImport("kernel32.dll")] public static extern UInt32 GetFirmwareEnvironmentVariableA([MarshalAs(UnmanagedType.LPWStr)] string...
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+ Theoretically, it should work on every BIOS and UEFI. Not restricted in terms by the BIOS/UEFI-vendor. (Yes, by BIOS I mean even legacy BIOS)
+ No BIOS/UEFI-Modding needed (I used this method for a Fujitsu Workstation with Aptio V UEFI, which is currently not NVMe moddable)
+ Easy updateable EFI. Changes to the configs can be made out of your favorite OS via text-editor.
(+) You can have a Hackintosh (Don't ask me for support on this, I never intended to have one, I'm just using the EFI-Loader + NVMExpress.efi driver.


- Slightly longer boot times (This can be decreased by changing values inside the config.plst

NOTE to Legacy BIOS users: I didn't try a Legacy BIOS installation yet, so the steps for you are just theoretical. Feedback is welcome and needed!

How does it work?:



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The new UEFI and the Legacy BIOS are two different modes of booting a Windows-based computer. Generally, the recent Windows 8/10 computers come with UEFI, while the older Windows 7/Vista computers usually come with Legacy BIOS. However, that is not absolute. Now if you want to know if your computer is using UEFI or BIOS, read this page to learn how to check it.

How to check if your computer uses UEFI or BIOS

Here are three methods, among which the first method applies to Windows 10/8/8.1 and the last two methods apply to all Windows versions including Windows 7, Vista, 8, 10, etc.

Method 1: by System Information

Step 1: Press Win + R to open Run dialog box. Then type MSinfo32 and click OK. This will open System Information.

Step 2: In the System Information window, locate the System Summary. Then on the right-side pane, find the BIOS Mode item. There it displays if your computer is using UEFI or Legacy BIOS mode.


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I am not able to migrate my Windows 8 or Windows 7 PC into a virtual machine using Parallels® Transporter™. Migration fails on detecting the operating system type.


Your PC most likely has a GPT partition on the hard drive and is using EFI/UEFI instead of BIOS.


Parallels Desktop supports migrating computers with GPT partitions and EFI/UEFI starting from version 10. Parallels Desktop 9 and earlier do not support migrating computers with GPT partitions and EFI/UEFI.

To determine whether your PC is using BIOS or EFI/UEFI please follow the steps below:

Start your PC.

Go to Start > Computer.

Navigate to C:\Windows\Panther\setupact.log.

Open setupact.log.

Search for this string:

Callback_BootEnvironmentDetect: Detected boot environment:

It should tell you whther the boot environment is BIOS or UEFI:

Code:Callback_BootEnvironmentDetect: Detected boot environment: BIOS...
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Long time Windows users might be well aware of the term – UEFI. For those who are not, UEFI is the abbreviated form of Unified Extensible Firmware Interface, a sort of BIOS replacement to set up the hardware and load and start an operating system. It was first introduced by Intel as Intel Boot Initiative which was later changed to EFI. Later, EFI was then taken over by the Unified EFI Forum and was therefore named as UEFI. UEFI comes with a boot manager which removes the needs for a separate boot loader. Besides, it gives you faster start-ups and better networking support. Most recent Windows PCs are shipped with UEFI support. To check if your PC supports and uses UEFI/EFI or BIOS, follow the steps highlighted below.

Check if your PC uses UEFI or BIOS

(1) Open File Explorer and navigate to the following folder: C:\Windows\Panther.

In the folder named Panther you will see a text file titled setupact.log. The file will automatically open in...

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This article explains EFI/UEFI computer and tell you how to determine if a PC is an UEFI PC or a BIOS PC.

UEFI is short for "Unified Extensible Firmware Interface". It’s an advanced interface standard of firmware for operating system compared to legacy BIOS, such as it supports fast PC startup, bootable GPT hard drive, larger capacity more than 2T etc. Almost all recent PCs are EFI/UEFI.

UEFI system architecture

The UEFI specification will be based on the EFI specification (Extensible Firmware Interface) published by Intel with corrections and changes managed by the Unified EFI Forum. UEFI is meant as a replacement for the BIOS firmware interface, present in all IBM PC-compatible personal computers. In practice, most UEFI systems have legacy support for BIOS functions. The UEFI specification is managed by the Unified EFI Forum.

Since UEFI-based computers have bootable information written in their motherboards, you may need to set...

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