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The quickest way to check is with System Information: press Win + R, enter msinfo32, press Enter, and read BIOS Mode under System Summary. UEFI means the current Windows session booted in UEFI mode; Legacy means it booted through Legacy BIOS or BIOS-compatibility mode.
Check UEFI mode with System Information
- Press Windows key + R.
- Type
msinfo32and press Enter. - Keep System Summary selected in the left pane.
- Find BIOS Mode.
| BIOS Mode | Meaning |
|---|---|
| UEFI | Windows is currently booted in UEFI mode. |
| Legacy | Windows is currently booted through Legacy BIOS or CSM compatibility mode. |
This checks how the current Windows installation booted—not merely whether the motherboard supports UEFI. On localized versions of Windows, the label may be translated. Use a normal Windows session where possible; Microsoft notes that System Information cannot provide hardware information in Safe Mode. See Microsoft’s UEFI verification guidance.
Check Secure Boot separately
In the same System Information window, find Secure Boot State:
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- Off: The system is using UEFI-capable firmware, but Secure Boot is disabled.
- Unsupported: The current boot mode, firmware, or hardware does not support Secure Boot.
Secure Boot is not the same as UEFI mode. A computer can show BIOS Mode: UEFI while Secure Boot is off.
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You can also run this command in an elevated Windows PowerShell window:
Confirm-SecureBootUEFITrue means Secure Boot is enabled, while False means it is supported but disabled. A message saying the cmdlet is not supported generally indicates a non-UEFI BIOS system or an unsupported platform. Access denied can mean PowerShell was not opened as administrator. This is a Secure Boot check, not a replacement for reading BIOS Mode. See Microsoft’s Confirm-SecureBootUEFI documentation.
Check whether the Windows disk is GPT or MBR
UEFI is a firmware boot mode. GPT and MBR are disk partition-table formats. They are related, but checking a disk’s partition style does not by itself prove how Windows booted.
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PowerShell
Open PowerShell and run:
Get-Disk | Format-Table Number, FriendlyName, PartitionStyle, OperationalStatus, SizeFind the disk containing the Windows installation and read PartitionStyle:
- GPT: GUID Partition Table.
- MBR: Master Boot Record.
Do not assume the Windows disk is always Disk 0. On a multi-drive computer, Windows may boot using files on one disk while the Windows volume is on another.
Disk Management
- Right-click Start and select Disk Management.
- Right-click the disk label, such as Disk 0, rather than an individual partition.
- Select Properties, then open the Volumes tab.
- Read Partition style.
DiskPart
Open Command Prompt or PowerShell as administrator and run:
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diskpart
list disk
exitAn asterisk in the GPT column indicates that a disk uses GPT. These commands only inspect the disks. Do not run destructive commands such as clean, convert gpt, or format merely to check the partition style. Microsoft’s MBR2GPT documentation also describes these disk-inspection methods.
How the results usually match
| BIOS Mode | Relevant disk style | Likely explanation |
|---|---|---|
| UEFI | GPT | Normal UEFI installation. |
| Legacy | MBR | Normal Legacy BIOS installation. |
| UEFI | MBR | Unusual or transitional configuration; inspect the boot files and system disk. |
| Legacy | GPT | Possible compatibility-mode boot or booting from another disk. |
| UEFI | Mixed disk styles | Windows may be booting from one disk while other disks use MBR. |
| UEFI | Secure Boot Off | UEFI is active; Secure Boot is simply disabled. |
The EFI System Partition or Windows boot files can be on a different physical disk from the C: volume. In dual-boot systems, this result describes how the current Windows installation booted, not necessarily how every operating system on the computer boots.
Other ways to investigate boot mode
Inspect firmware boot entries
For advanced troubleshooting, run:
bcdedit /enum firmwareOn many UEFI systems, Windows Boot Manager references an EFI path such as EFIMicrosoftBootbootmgfw.efi. BCD output varies by firmware and can be difficult to interpret, so msinfo32 remains the preferred check.
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Check from Windows Setup or WinPE
When working in Windows Preinstallation Environment or Windows Setup—not an ordinary desktop Windows session—Microsoft documents this registry check:
reg query HKLMSystemCurrentControlSetControl /v PEFirmwareTypeIn WinPE, 0x1 means BIOS and 0x2 means UEFI. This is a WinPE/Setup method and is not the normal command for checking an installed Windows desktop. See Microsoft’s firmware-mode documentation.
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UEFI firmware menus may show settings named CSM Support, Legacy Support, Legacy Boot, UEFI and Legacy, UEFI Only, or Windows UEFI Mode. These settings describe what the firmware permits or prefers. msinfo32 confirms how Windows actually booted.
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Firmware hotkeys and menu names vary by manufacturer. Do not change from Legacy to UEFI simply because the motherboard supports UEFI. If Windows is installed on an MBR disk, switching the firmware first can make the installation unbootable.
In a virtual machine, msinfo32 reports the firmware mode presented to the guest. It does not necessarily describe the physical host’s firmware.
What to do if BIOS Mode says Legacy
Legacy mode is not automatically a problem. An older installation can work normally this way. Conversion is worth considering when you need Secure Boot, UEFI-only firmware operation, certain Windows 11 security configurations, or a modern deployment standard.
For supported Windows 10 and Windows 11 installations, Microsoft’s MBR2GPT.exe can convert a system disk from MBR to GPT without intentionally deleting user data. It is not risk-free and has layout, encryption, partition, and firmware prerequisites.
- Back up important files and prepare a recovery method.
- If BitLocker is enabled, save the recovery key and suspend protection where appropriate.
- Identify the correct system-disk number. Do not assume it is Disk 0.
- Validate the disk first, replacing
0with the correct number:mbr2gpt.exe /validate /disk:0 /allowFullOS - Only if validation succeeds, run:
mbr2gpt.exe /convert /disk:0 /allowFullOS - Restart into firmware settings and change the boot mode to UEFI or UEFI Only, using the manufacturer’s terminology.
- After Windows starts, run
msinfo32again and confirm BIOS Mode: UEFI. - Confirm the system disk is GPT. Enable Secure Boot only after Windows successfully boots in UEFI mode and you have prepared for a possible BitLocker recovery prompt.
MBR2GPT is intended for system disks and validates prerequisites before conversion, but validation does not eliminate the need for backups. If validation fails, or the installation is damaged, the disk is being replaced, or you have a complete backup and do not need to preserve the existing installation, a clean UEFI installation may be simpler. A clean installation can erase existing partitions and data. See Microsoft’s Windows Setup guidance for MBR and GPT.
If msinfo32 does not open
- Run it from a normal Windows session rather than Safe Mode.
- Search Start for System Information.
- Use PowerShell, Disk Management, or DiskPart for secondary evidence.
- Do not infer the boot mode from the motherboard logo, boot speed, or whether the computer supports UEFI.
For the primary answer, return to System Information → System Summary → BIOS Mode. That value is the clearest indication of how the currently running Windows installation booted.
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