Difference Between Legacy BIOS and UEFI
Interface, boot speed, disk limit and why Windows 11 requires UEFI.
Both are the most basic program on your computer, the one that starts before any operating system — but UEFI is the modern evolution of classic BIOS, with real differences that affect what you can do.
| BIOS (legacy) | UEFI | |
|---|---|---|
| Interface | Text only, navigated with keyboard | Graphical, supports mouse |
| Boot speed | Slower | Faster |
| Maximum compatible disk size | 2 TB (with MBR partition) | No practical limit (GPT) |
| Boot security | Not available | Secure Boot |
| Windows 11 machines | Not compatible | Mandatory requirement |
Which one do you have?
If your computer is from the last few years and comes with Windows
11, you almost certainly have UEFI — it's a requirement to install it.
To confirm: Windows + R → msinfo32 → look for
"BIOS Mode" in the window that opens. It will say "UEFI" or "Legacy".
Can I switch from one to the other?
Technically yes, but it involves converting the disk between MBR and GPT formats, a delicate process that may require reinstalling Windows. It isn't something to change "just because" — it only makes sense if you specifically need a feature only one of the two offers (like installing Windows 11 on a machine with old legacy BIOS).
We already mentioned BIOS/UEFI in our guide on dual booting Linux and Windows — this is exactly where you go to turn off Secure Boot if the Linux installer won't start.
Tip: you don't need to understand the entire BIOS/UEFI to use your computer normally — most people only go in there at specific moments (installing an operating system, changing the boot order), not as part of daily use.
Frequently asked questions
Does Windows 11 work with legacy BIOS?
No, Windows 11 requires UEFI as one of its official installation requirements, along with TPM 2.0. A machine with only legacy BIOS doesn't meet the requirements without a prior disk conversion.
Is it dangerous to go into the BIOS/UEFI?
Just looking doesn't change anything — it's safe to go in and out without touching any option. The risk appears if you modify settings without knowing what they're for, so only change what you specifically need.
How do I enter my computer's BIOS/UEFI?
Normally by pressing a specific key (F2, F12, Delete, or similar) right when turning on the machine, before Windows loads. The exact key varies by manufacturer — it's usually shown briefly on screen during startup.