What BIOS is and when you need to open it

BIOS (Basic Input/Output System) is the software that runs on your computer before Windows or macOS loads. It controls hardware settings like boot order, fan speed, and whether certain ports work. You access BIOS through a setup screen that appears during startup — usually by pressing a specific key like Delete, F2, or F12 while your computer is turning on.

Most people never need to open BIOS. But if you're troubleshooting a hardware problem, changing which drive your computer boots from, or adjusting fan settings to reduce overheating, BIOS is where you make those changes. It's also where you can enable or disable built-in features like USB ports or the camera.

The exact key to press varies by manufacturer. Dell, Lenovo, HP, and Asus each use different keys. If you press the wrong key, your computer will just boot normally — no harm done. You can try again on the next restart.

Key Takeaways

  • BIOS is accessed by pressing a specific key during startup, usually Delete, F2, F10, or F12, depending on your computer's manufacturer.
  • The correct key is often shown on the boot screen for a few seconds, or you can find it in your computer's manual or the manufacturer's website.
  • Changes you make in BIOS take effect when ready and persist until you change them again — there is no "save and exit" button like in other programs.
  • If you change a setting and your computer stops working properly, you can reset BIOS to factory defaults from within the setup screen itself.

How to find the correct key for your computer

The easiest way is to watch your screen during startup. Most computers display a message like "Press Delete to enter Setup" or "Press F2 for BIOS" for a few seconds before Windows loads. Write down the key shown.

If you miss the message, check your computer's manual or the manufacturer's support website. Search for "[Your computer model] BIOS key" — for example, "Dell XPS 13 BIOS key" or "HP Pavilion BIOS key". The manufacturer's site will have the answer.

Common keys by brand: Dell uses F2 or Delete; HP uses F10 or Esc; Lenovo uses F2 or Enter; Asus uses Delete or F2; Acer uses Delete or F2. If you own a custom-built PC, the key depends on the motherboard manufacturer, which is usually listed in your documentation.

Step-by-step: Getting into BIOS

Shut down your computer completely. Do not use sleep or hibernate — actually turn it off.

Turn the computer back on. when ready start pressing your BIOS key repeatedly — about once per second. Press it many times in the first few seconds after power-on. If you press too late, Windows will load and you'll have to restart and try again.

The BIOS setup screen should appear. It looks different from Windows or macOS — usually a dark background with white or blue text, organized into menus. You navigate using arrow keys and Enter. Do not use your mouse; BIOS does not respond to it.

If Windows loads instead, you pressed the key too late or the wrong key. Shut down and try again, pressing the key faster and more often during the first few seconds of startup.

What you can change and what to leave alone

Safe changes include boot order (which drive loads first), fan speed settings, and disabling hardware you don't use (like an integrated camera or Bluetooth). These changes won't break your computer — they just change how it behaves.

Avoid changing settings you don't recognize. Changing CPU voltage, memory timing, or security settings without knowing what you're doing can cause crashes or prevent your computer from starting. If you accidentally change something and your computer stops working, restart and go back into BIOS to reset everything to defaults — there is usually a "Load Defaults" or "Reset to Factory Settings" option in the main menu.

One common safe change: if your computer is overheating, you can increase fan speed in the thermal or cooling section. Higher fan speed means more noise but better cooling. Lower fan speed is quieter but runs hotter.

How to exit BIOS and save your changes

Look for an option called "Save and Exit" or "Exit and Save Changes" — usually at the bottom of the main menu or in a separate menu. Press Enter on that option. BIOS will ask you to confirm; select "Yes" and your changes take effect when ready.

If you want to leave without saving, look for "Exit Without Saving" or "Discard Changes". Your computer will restart with no changes made.

Some BIOS versions use function keys instead of menu options. Look at the bottom of the screen for text like "F10 to Save" or "Esc to Exit". Follow the on-screen instructions.

Resetting BIOS if something goes wrong

If you changed a setting and your computer now won't start or behaves strangely, go back into BIOS and look for "Load Defaults", "Reset to Factory Defaults", or "Restore Defaults". Select that option, confirm, and save. This erases all your changes and returns BIOS to how it came from the factory.

If your computer won't start at all and you can't get into BIOS, there is a physical reset. Shut down completely, unplug the power cable, and wait 30 seconds. Open the case (if you're comfortable doing so) and look for a small battery on the motherboard — it looks like a coin. Remove it for 10 seconds, then put it back. This clears BIOS memory. Plug in the power and restart.

If you're not comfortable opening the case, contact the manufacturer's support line or take the computer to a repair shop. A technician can reset BIOS in minutes.

BIOS vs. UEFI: What's the difference

Newer computers use UEFI (Unified Extensible Firmware Interface) instead of traditional BIOS. UEFI does the same job but looks more modern — it may have a graphical interface with a mouse, colors, and buttons instead of text menus.

The process is the same: restart, press the same key during startup, make your changes, and save. The menus are organized differently, but the settings are in similar places. If your computer has UEFI, the startup screen will say "UEFI Setup" or "UEFI Firmware Settings" instead of "BIOS Setup".

For your purposes, BIOS and UEFI work the same way. The instructions above explore to both.

Frequently Asked Questions

What happens if I press the wrong key during startup?

Nothing. Your computer will just boot normally into Windows or macOS. You can restart and try the correct key on the next boot. There is no penalty for pressing the wrong key.

Can I access BIOS from within Windows?

On newer Windows computers, yes. Go to Settings > System > Recovery, then click "Restart now" under "Advanced startup". Choose "Troubleshoot" > "Advanced options" > "UEFI Firmware Settings". On older computers or Macs, you must restart and press the key during startup.

Will changing BIOS settings slow down my computer?

Most changes have no effect on speed. Lowering fan speed might make your computer run slightly hotter, which could cause it to throttle (reduce performance to cool down). Increasing fan speed uses a tiny bit more power but won't slow you down.

Is it safe to change boot order?

Yes. Changing which drive your computer boots from is one of the safest BIOS changes you can make. You might do this to boot from a USB drive or to prioritize an external hard drive. You can always change it back.

What if I forget to save my changes before exiting BIOS?

If you exit without saving, your changes are discarded and your computer boots with the old settings. You'll need to go back into BIOS and make the changes again, then save this time.