What BIOS is and why you might need to change it

BIOS (Basic Input/Output System) is firmware — low-level software that runs before your operating system loads. It controls how your hardware talks to Windows, macOS, or Linux, and handles things like boot order, fan speed, and security settings. Most people never touch BIOS, but you might need to enter it to change which drive your computer boots from, enable or disable hardware features, update security patches, or troubleshoot hardware problems.

The process differs slightly depending on whether you have a Windows PC, Mac, or Linux machine, and whether your computer uses traditional BIOS or the newer UEFI firmware (which works the same way from a user perspective). The steps below cover the most common scenarios.

Key Takeaways

  • You enter BIOS by restarting your computer and pressing a specific key during startup — usually Delete, F2, F10, or F12, depending on your manufacturer.
  • On Windows PCs, you can also reach BIOS through Settings > System > Recovery > Advanced Startup without restarting immediately.
  • On Macs, restart and hold Command + Option + P + R to reset NVRAM, or Command + Option + R to enter Recovery Mode, which gives you firmware access.
  • Write down any settings you change before you make them, so you can reverse the change if something breaks.
  • If you do not know what a setting does, leave it alone — incorrect BIOS changes can prevent your computer from starting.

Entering BIOS on a Windows PC

The fastest way is to restart your computer and press a key during the startup sequence. The key varies by manufacturer: Dell and HP use F2, Lenovo uses F2 or Enter, ASUS uses Delete, and MSI uses Delete. If you are not sure, restart and watch the first screen — it usually displays the correct key in small text at the bottom.

If you miss the window or want to avoid the restart, Windows 10 and 11 offer an alternative. Open Settings, go to System, then Recovery. Under Advanced Startup, click Restart Now. Your computer will restart into a blue menu. Choose Troubleshoot, then Advanced Options, then UEFI Firmware Settings. Click Restart, and you will enter BIOS without having to time a key press.

Once you are in BIOS, use the arrow keys to navigate and Enter to select. The layout varies, but you will usually see tabs or menus at the top. Read what you are changing before you change it. When you are done, look for an option to Save and Exit — usually at the bottom of the screen or in a separate menu.

Entering BIOS on a Mac

Macs do not have a traditional BIOS menu like Windows PCs. Instead, they use firmware settings that you access differently depending on whether your Mac has an Intel processor or Apple Silicon (M1, M2, M3, etc.).

On Intel Macs, restart and immediately hold Command + Option + R. This boots into Recovery Mode, where you can access firmware settings through the Utilities menu. On Apple Silicon Macs, restart and hold the power button until you see the startup options screen. Click Options, then continue to Recovery Mode. From there, go to Utilities > Firmware Security to adjust settings.

Most Mac users never need to change firmware settings. Common reasons include disabling external boot (for security) or resetting NVRAM if your Mac is behaving oddly. If you are unsure whether you need to be in firmware settings, you probably do not.

Entering BIOS on a Linux machine

Linux computers use the same BIOS or UEFI firmware as Windows machines, so the entry method is identical: restart and press Delete, F2, F10, or F12 depending on your hardware manufacturer. The difference is that Linux does not provide a graphical shortcut like Windows does, so you must time the key press during startup.

If you are running Linux on a virtual machine, you may not have access to BIOS at all — the host operating system controls the firmware. Check your virtualization software's documentation to see whether it exposes BIOS settings to the guest system.

Common BIOS settings and what they do

Boot Order determines which drive your computer checks first when it starts. If you are installing a new operating system from a USB drive, you may need to move USB to the top of the boot order. After installation, move your hard drive back to the top so your computer boots normally.

Secure Boot is a security feature that prevents unauthorized software from loading during startup. It is on by default on most new Windows PCs. Turning it off can make your computer less secure, but some older Linux distributions or custom setups require it to be off. Only disable it if you have a specific reason.

Fan Control lets you adjust how aggressively your cooling fans run. The default setting (usually "Auto") is fine for most people. Changing it can make your computer louder or hotter, so leave it alone unless you are troubleshooting overheating.

Virtualization (VT-x on Intel, AMD-V on AMD) allows your computer to run virtual machines more efficiently. It is usually off by default. Turn it on only if you plan to use virtualization software like VirtualBox or VMware.

What to do if you change something and your computer will not start

If a BIOS change breaks your startup, you have a few options. The simplest is to restart, enter BIOS again, and change the setting back. If you cannot remember what you changed, look for a Reset to Defaults option in the BIOS menu — this restores all settings to factory state, though you will lose any customizations you made.

On some computers, you can reset BIOS by removing the CMOS battery from the motherboard for a few minutes, then reinserting it. This is a last resort and requires opening your computer's case. If you are not comfortable doing that, contact the manufacturer's support line or take the computer to a repair shop.

If your computer will not enter BIOS at all, the problem is likely hardware-related, not a BIOS setting. Try a different keyboard, or contact support.

When you should not change BIOS yourself

If your computer is under warranty and you are not sure what you are doing, contact the manufacturer before making changes. Some BIOS modifications can void your warranty, and a technician can often do it for you without risk.

If you are trying to fix a problem and you do not know which setting controls it, do not guess. Search for the specific problem plus your computer model, or ask in a support forum. A wrong change can take hours to undo.

Never update BIOS firmware unless your manufacturer specifically recommends it for a problem you are experiencing. BIOS updates are rare and usually only necessary for security patches or hardware compatibility. A failed update can brick your computer.

Frequently Asked Questions

What is the difference between BIOS and UEFI?

UEFI is the newer standard that replaced traditional BIOS. From a user perspective, they work the same way — you enter the menu the same way and change settings the same way. UEFI is more secure and supports larger hard drives. Most computers made after 2010 use UEFI, though the menu is often still called BIOS.

Can I change BIOS settings from within Windows?

No. BIOS runs before Windows loads, so Windows cannot modify it. You must restart your computer and enter the BIOS menu directly. Some manufacturers provide Windows utilities that change BIOS settings, but these restart your computer into BIOS automatically.

Will changing BIOS settings make my computer faster?

Not meaningfully. Overclocking (pushing your processor faster) is possible in BIOS on some machines, but it voids warranties, generates heat, and risks hardware damage. For most users, BIOS changes are for troubleshooting or enabling specific features, not performance.

What if I forgot my BIOS password?

If you set a BIOS password and forgot it, you will need to reset BIOS to factory defaults. This usually means removing the CMOS battery from the motherboard for a few minutes. If you are not comfortable opening your computer, contact the manufacturer or a repair shop — they can reset it for you.

Is it safe to update BIOS?

BIOS updates are generally safe if your computer is plugged into power and you follow the manufacturer's instructions exactly. The risk is very small on modern computers. Only update if the manufacturer recommends it for a specific reason, like a security patch or hardware compatibility fix. Do not update out of curiosity.