What BIOS is and why you might need to open it

BIOS (Basic Input/Output System) is the software that runs on your computer before Windows, Mac OS, or Linux starts up. It controls which hard drive your computer boots from, how much power goes to your fan, and whether your keyboard and mouse work during startup. You open BIOS by pressing a specific key during the moment your computer is turning on — before the operating system loads.

Most people never need to open BIOS. But if you're troubleshooting a hardware problem, installing a new drive, or trying to boot from a USB stick, you'll need to get in. The key you press depends on your computer's manufacturer and can be F2, F10, F12, Delete, or Escape — and you have only a few seconds to press it.

Key Takeaways

  • You enter BIOS by restarting your computer and pressing a specific key (usually F2, F10, F12, Delete, or Escape) during the startup screen, before Windows or Mac OS loads.
  • The correct key depends on your computer's brand — Dell, HP, Lenovo, and others use different keys, and your startup screen usually displays which one to press.
  • BIOS controls hardware settings like boot order, fan speed, and which drive your computer starts from, but changing the wrong setting can prevent your computer from starting.
  • If you miss the window to press the key, restart your computer and try again — you have only a few seconds after the manufacturer's logo appears.
  • Write down any settings you change before you change them, so you can reverse the change if something goes wrong.

How to enter BIOS on Windows computers

Restart your computer. As soon as you see the startup screen — usually a logo from Dell, HP, Lenovo, Asus, or another manufacturer — look for text that says "Press [key] to enter Setup" or "Press [key] to enter BIOS." The key will be listed right there. Press it repeatedly (don't hold it down) until the BIOS menu appears. You have only a few seconds, so be ready.

If you miss the window, your computer will finish starting Windows normally. Restart and try again. Common keys are F2, F10, F12, and Delete. If the startup screen doesn't tell you which key to press, try F2 first — it works on most Dell and Lenovo machines. If that doesn't work, restart and try F10 or Delete.

Some newer computers use a different method. If pressing keys during startup doesn't work, restart Windows, hold Shift, and click "Restart." This takes you to a blue menu. Click "Troubleshoot," then "Advanced Options," then "UEFI Firmware Settings." Your computer will restart into BIOS.

How to enter BIOS on Mac computers

Apple calls BIOS "firmware" and handles it differently than Windows machines. Shut down your Mac completely. Turn it back on and when ready press and hold Command + R until you see the Apple logo or a spinning globe. This takes you to Recovery Mode, not BIOS itself.

From Recovery Mode, click "Utilities" in the menu bar, then "Firmware Password Utility" if you need to change firmware settings. Most Mac users never need to open firmware settings — Apple handles hardware management automatically. If you're trying to boot from a USB drive or external hard drive, restart and hold Option instead of Command + R, and your Mac will show you a list of drives to choose from.

What you'll see inside BIOS and what not to change

BIOS menus vary by manufacturer, but most show tabs or categories like "Main," "Advanced," "Boot," "Security," and "Exit." The Main tab shows your hardware — hard drive model, amount of RAM, processor type. The Boot tab controls which drive your computer starts from first. The Advanced tab contains settings for fans, power management, and other hardware features that most people should leave alone.

Do not change settings you don't understand. Changing the wrong setting — like disabling a SATA port or changing CPU voltage — can prevent your computer from starting at all. If you're in BIOS to troubleshoot a specific problem, change only the one setting you came to change. Write down what the setting was before you change it, so you can change it back if needed.

Changing boot order to start from a USB drive

If you need to install Windows from a USB stick or run a repair tool, you'll change the boot order. Insert your USB drive, restart your computer, and enter BIOS. Navigate to the Boot tab (the name varies — it might say "Boot Options" or "Boot Priority"). You'll see a list of drives in order: usually your hard drive is first, and your USB drive appears lower in the list.

Use the arrow keys to highlight your USB drive, then press Enter or use the + and - keys to move it to the top of the list. Save your changes — usually by pressing F10 or navigating to "Exit" and choosing "Save and Exit." Your computer will restart and boot from the USB drive. After you're done, restart, enter BIOS again, and move your hard drive back to the top of the boot order.

Saving your changes and exiting BIOS

When you're done making changes, look for an "Exit" tab or menu. You'll usually see options like "Save and Exit," "Exit Without Saving," or "Discard Changes and Exit." Choose "Save and Exit" if you made changes you want to keep. Choose "Exit Without Saving" if you changed something and want to undo it. Your computer will restart with your new settings in place.

If your computer won't start after you changed a BIOS setting, restart and enter BIOS again. Look for an option called "Load Defaults," "Reset to Defaults," or "Restore Factory Settings." This puts all BIOS settings back to how they came from the manufacturer. You'll lose any changes you made, but your computer should start normally again.

Common reasons to open BIOS and what to change

The most common reason is to change boot order so you can start from a USB drive — covered above. Another reason is to check how much RAM your computer has or what hard drive model it uses, which you can see in the Main tab without changing anything. Some people open BIOS to enable or disable hardware features — like turning off the built-in camera or microphone for privacy, or disabling a USB port that isn't working.

If your computer is overheating, you might open BIOS to check fan speed settings, though most computers manage this automatically now. If you're installing a new hard drive and your computer doesn't recognize it, you might need to enable the SATA port it's plugged into in the Advanced tab. In all these cases, change only the specific setting you need, and write down the old value first.

Frequently Asked Questions

What if I press the key but nothing happens?

You may have pressed it too late — BIOS only responds during the first few seconds of startup, before the operating system begins loading. Restart your computer and watch for the manufacturer's logo, then press the key as soon as you see it. If the startup screen shows a different key to press, use that one instead.

Can I damage my computer by opening BIOS?

Opening BIOS itself is safe — you're just looking at settings. Changing the wrong setting can prevent your computer from starting, but you can always restart and use "Load Defaults" to undo your changes. Do not change anything unless you know what it does.

Why does my computer ask for a password when I try to enter BIOS?

Someone set a BIOS password on your computer, usually for security. If it's your computer and you forgot the password, contact the manufacturer's support line with proof of ownership. If it's a work computer, contact your IT department.

Is BIOS the same as UEFI?

UEFI is the newer version of BIOS and works the same way from a user's perspective — you still press a key during startup to enter it, and the menus look similar. Most computers made in the last ten years use UEFI instead of older BIOS, but the terms are often used interchangeably.

Do I need to open BIOS to upgrade my RAM or hard drive?

No. You can physically install new RAM or a hard drive without touching BIOS — your computer will recognize the new hardware automatically when it starts up. You might open BIOS afterward just to confirm the new hardware appears in the Main tab, but you don't need to change any settings.