UEFI and Legacy BIOS are two ways a PC can start an operating system. To check which mode your current Windows installation uses, open System Information and read the BIOS Mode entry. You do not need to enter the firmware settings or change anything to perform this check.
This guide explains how to read that result, how it relates to Secure Boot, and why changing a boot setting can require more preparation than flipping a switch.
Technical information checked: October 16, 2026.
How to Check BIOS Mode in Windows
- Press Windows + R.
- Type
msinfo32and press Enter. - Select System Summary.
- Find BIOS Mode and record whether it says UEFI or Legacy.
- Record Secure Boot State separately.
These are status checks. Opening System Information does not change your boot configuration.
UEFI vs Legacy BIOS: What Is the Difference?
UEFI stands for Unified Extensible Firmware Interface. It is the modern firmware interface used to start Windows on current PCs. Legacy BIOS refers to the older startup approach; some UEFI firmware also offers a compatibility mode for older installations.
| Check | UEFI | Legacy BIOS |
|---|---|---|
| BIOS Mode in System Information | UEFI | Legacy |
| Secure Boot | Can support Secure Boot; check whether it is enabled. | Secure Boot is unavailable in Legacy boot mode. |
| Typical Windows system-disk layout | GPT | MBR |
| What the result tells you | The current Windows installation started in UEFI mode. | The current installation started in Legacy mode; this alone does not establish the motherboard's full capabilities. |
What Is CSM?
CSM means Compatibility Support Module. On firmware that offers it, this provides support for legacy startup behavior. Manufacturers may use labels such as Legacy Support, CSM, or Boot Mode in their setup menus.
Menu names and available combinations differ between motherboards. Use instructions for your exact device instead of assuming that a setting shown in another PC's tutorial exists on yours.
Does UEFI Mean Secure Boot Is Enabled?
No. BIOS Mode and Secure Boot State answer different questions. UEFI identifies the startup mode; Secure Boot State reports whether the security feature is active.
- UEFI and On: Windows reports UEFI startup with Secure Boot enabled.
- UEFI and Off: Windows reports UEFI startup, but Secure Boot is disabled.
- Legacy and Unsupported: Investigate the boot configuration and manufacturer documentation before concluding that the hardware lacks UEFI support.
For the difference between startup verification and TPM security functions, read our TPM 2.0 vs Secure Boot guide.
How GPT and MBR Relate to Boot Mode
GPT and MBR describe disk partition layouts. UEFI and Legacy describe boot modes. They are related concepts, but they are not interchangeable names for the same setting.
For standard Windows installations, UEFI startup uses a GPT system disk, while Legacy startup uses MBR. A separate data drive does not tell you how Windows itself boots.
Microsoft explains this relationship in its Windows Setup partition-style documentation.
Can You Just Switch Legacy to UEFI?
Do not assume the existing Windows installation will start after a firmware-only change. The boot files and system-disk layout must support the selected mode.
Microsoft provides MBR2GPT for converting eligible Windows system disks. It checks prerequisites, and not every configuration qualifies. A successful conversion also requires the appropriate firmware boot configuration afterward.
Before planning a change, back up important files, make sure any encryption recovery key is accessible, and review the manufacturer instructions. Read Microsoft's MBR2GPT documentation for conversion requirements and BitLocker considerations.
This article is a status-checking guide, not a universal disk-conversion procedure.
Why Boot Mode Matters for PC Gaming
When a game's support instructions mention Secure Boot, recording BIOS Mode helps explain the starting configuration. However, a UEFI result alone does not confirm that every game requirement is satisfied.
Use the exact error message and publisher instructions when troubleshooting. Our PC game anti-cheat compatibility database provides a starting point for the games covered by our guides.
What to Record Before Asking for Help
- Your PC or motherboard model.
- Your Windows version and build.
- The BIOS Mode and Secure Boot State entries.
- The exact error message.
- Whether the problem began after a firmware change or Windows reinstall.
Send the relevant details to support rather than posting a complete system-information export publicly. Keep encryption recovery keys private.
Frequently Asked Questions
Can I check boot mode without restarting?
Yes. Open msinfo32 in Windows and check BIOS Mode under System Summary.
Does Legacy mean I need a new motherboard?
Not necessarily. The entry describes the current startup mode. Check the manufacturer's specifications to establish what the hardware supports.
Should I disable CSM immediately?
No. First establish whether your Windows installation supports UEFI startup and consult your device documentation.
Does changing boot mode automatically enable TPM 2.0?
Do not use boot mode as proof of TPM status. Check TPM separately using the steps in our TPM and Secure Boot guide.