What BIOS is and when you need to open it
BIOS (Basic Input/Output System) is firmware that runs before your operating system loads. It controls hardware settings like boot order, fan speed, and security features. Most people never need to open it, but you might if you're troubleshooting hardware problems, changing how your computer starts up, or updating security settings.
The BIOS sits between your computer's power button and Windows or macOS loading. It's the first thing that runs when you turn on your machine. You access it by pressing a specific key during the startup sequence — before your operating system appears on screen.
If you're not sure whether you need BIOS access, you probably don't. But if someone has told you to change a BIOS setting, or you're trying to boot from a USB drive or external hard drive, these instructions will get you there.
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.
- The key you need varies by brand: Dell and HP often use F2, Lenovo uses F1 or F2, ASUS uses Delete, and Acer uses Delete or F2.
- You must press the key repeatedly as soon as the computer powers on, before the Windows or macOS logo appears.
- BIOS changes can prevent your computer from starting, so only change settings if you know what they do or someone has given you specific instructions.
How to enter BIOS on a Windows PC
Restart your computer. As soon as it powers back on — before you see the Windows logo — begin pressing the correct key for your manufacturer. You'll see a brief moment of black screen with text; that's when you press.
The key varies by brand. Check the table below for your computer's manufacturer. If you're not sure which brand you have, look at the logo on the lid or the boot screen that appears before Windows loads.
| Manufacturer | Key to Press |
|---|---|
| Dell | F2 or Delete |
| HP / Compaq | F2 or Esc then F2 |
| Lenovo (ThinkPad) | F1 or Enter then F1 |
| ASUS | Delete or F2 |
| Acer | Delete or F2 |
| MSI | Delete |
| Gigabyte | Delete |
If you miss the window, let the computer finish loading Windows, then restart and try again. You may need to press the key multiple times in quick succession. Some computers also show a message like "Press F2 to enter Setup" — that's your signal to press that key.
How to enter BIOS on a Mac
Macs don't have a traditional BIOS in the same way Windows PCs do. Instead, they use firmware settings (or EFI on older Macs). The process depends on whether your Mac has an Apple Silicon chip (M1, M2, M3) or an Intel processor.
For Apple Silicon Macs (M1 and newer): Shut down your Mac completely. Press and hold the power button until you see "Loading startup options." Click "Options," then "Continue." You'll be asked to enter your password. This takes you to the firmware settings, not a traditional BIOS menu.
For Intel Macs (older models): Shut down your Mac. Turn it back on and immediately hold Command + R until you see the Apple logo. This opens Recovery Mode, where you can access some firmware settings through Utilities menu. For deeper firmware access on Intel Macs, you may need to use third-party tools or contact Apple Support.
What you'll see once you're in BIOS
The BIOS screen looks different depending on your manufacturer, but the layout is usually similar. You'll see text menus with options like "Main," "Advanced," "Boot," "Security," and "Exit." Use your arrow keys to navigate and Enter to select. Some newer BIOS interfaces use a mouse.
Common settings you might encounter include boot order (which device starts first), secure boot (a security feature), and hardware monitoring (fan speeds, temperatures). Don't change anything unless you have specific instructions, because the wrong change can prevent your computer from starting.
To leave BIOS without saving changes, look for "Exit" or "Discard Changes" and select it. To save and exit, choose "Save and Exit" or "Save Changes and Exit." Your computer will restart and load your operating system normally.
Changing boot order to start from a USB drive
One of the most common reasons to enter BIOS is to boot from a USB drive — for example, to install Windows, run a repair tool, or use a Linux live environment. Once you're in BIOS, look for a menu called "Boot," "Boot Order," or "Boot Priority."
In that menu, you'll see a list of devices: your hard drive, CD/DVD drive (if you have one), USB ports, and sometimes network boot. Use the arrow keys to move your USB drive to the top of the list, then save and exit. Your computer will restart and load from the USB drive instead of your hard drive.
If your USB drive doesn't appear in the boot list, it may not be recognized. Try a different USB port, or restart the computer with the USB drive already plugged in before you press the BIOS key.
Troubleshooting if you can't get into BIOS
If you're pressing the key and nothing happens, you may be pressing it too late. The window to enter BIOS is very short — sometimes less than a second. Try restarting again and pressing the key as soon as you see any text on screen, before the manufacturer's logo appears.
If your computer has a password-protected BIOS, you won't be able to enter without the password. If you don't know it, you may need to contact the manufacturer or a technician. Some manufacturers have master passwords, but they're not public.
On newer computers with Secure Boot enabled, you may need to disable it first to boot from certain USB drives. This is a security feature, and disabling it should only be done if you trust the device you're booting from.
When not to change BIOS settings
BIOS controls fundamental hardware behavior. Changing the wrong setting can make your computer unbootable, cause data loss, or create stability problems. Only change BIOS settings if you have clear instructions from a technician, a manufacturer's support page, or a trusted guide specific to your problem.
Common mistakes include disabling essential hardware, changing power settings incorrectly, or enabling features your computer doesn't support. If you make a change and your computer stops working, restart and go back into BIOS to undo it — most BIOS menus have a "Load Defaults" or "Reset to Defaults" option that restores safe settings.
Frequently Asked Questions
Is it safe to go into BIOS?
Simply entering BIOS and looking around is safe — you won't break anything by reading. The risk comes from changing settings you don't understand. If you only navigate the menus and exit without saving, your computer will work exactly as before.
Can I access BIOS from Windows without restarting?
On newer Windows 10 and 11 computers, you can go to Settings > System > Recovery > Advanced Startup and click "Restart Now." This gives you a menu to enter BIOS without a full restart. On older computers, you must restart and press the key during startup.
What if I forgot to press the key and Windows already loaded?
Restart your computer and try again. The BIOS key window only appears during the startup sequence, before Windows loads. You can't enter BIOS from within Windows on most computers.
Will changing BIOS settings delete my files?
Most BIOS changes won't delete files, but some can prevent your computer from starting, which makes your files temporarily inaccessible. Never change boot order or security settings unless you know what you're doing. If your computer won't start after a BIOS change, restart and undo the change.
Do I need to enter BIOS to install Windows?
Yes, usually. You'll need to change the boot order so your computer starts from the Windows installation USB drive instead of your hard drive. Once Windows is installed, you can change the boot order back.