What is the BIOS or UEFI, and should I ever update it?
The layer underneath Windows: what it does, how to get into it, the handful of settings that actually matter to a home user, and the honest answer on whether to update it.
- Difficulty
- intermediate
- Time
- 25 min
- Read
- 6 min
- Safety
- warning
Short answer
The BIOS or UEFI is the small program built into the motherboard that starts the machine and hands over to Windows. You reach it by pressing a key at power-on — usually F2, F10, F12, Del or Esc depending on the maker. For a home user there are about five settings in it that ever matter, and firmware updates should be done only when you have a specific reason: a fault the manufacturer's release notes name, a security advisory, or a new part the board does not recognise.
Every computer has firmware: a program stored on the motherboard itself that runs before any operating system exists. It powers up the components, tests them, decides what to start from, and hands over. On older machines this was called the BIOS; on everything modern it is UEFI, which does the same job with a graphical settings screen, support for large drives, and a security feature called Secure Boot. People use the two names interchangeably and the setup key is the same either way. Understanding it matters because a surprising number of frightening faults — a machine that will not boot, a drive Windows cannot see, an operating system that will not install — are settings on this screen rather than broken hardware.
Safety
Step by step
- Learn how to get into it on your machine.Power on and press the setup key repeatedly from the first second. F2 is the most common on laptops, F10 on HP, F1 or the small Novo button on Lenovo, Del on most desktop motherboards. There is usually a prompt for about a second under the logo. From inside Windows you can also go via Recovery, Advanced startup, Troubleshoot, UEFI Firmware Settings, which avoids the timing entirely.
- Know that looking is free.Entering the setup screen and leaving with Exit Without Saving changes nothing. Nothing in this guide asks you to change a setting blind, and the fear of "breaking something by going in" costs people money at repair shops for problems they could see in thirty seconds.
- Understand the boot order.This is the list of devices the firmware tries in turn. It is what you change to boot from a USB stick, and it is what has gone wrong when a machine ignores its own drive. Most machines also have a one-time boot menu on a separate key — often F12 — which is safer than changing the permanent order.
- Recognise Secure Boot and what it is for.It refuses to start boot code that is not signed by a trusted authority, which blocks a real class of attack. It also blocks some Linux installations and some older tools, which is why guides tell people to turn it off. Turning it off weakens the machine, and Windows 11 expects it on — so turn it back on afterwards.
- Know where the storage mode setting is.A setting variously called SATA mode, storage mode, AHCI or RAID or Intel RST. Changing it makes an installed Windows unbootable instantly, and it is the cause of a good proportion of "no bootable device" messages after someone has been in the firmware. If you have changed it, change it back.
- Use the firmware's own hardware tests.Most laptop makers build a memory and drive test into the firmware or into a separate diagnostics key at power-on. It runs without Windows, which makes it the honest test when Windows is the thing misbehaving.
- Decide about firmware updates on evidence, not habit.The three good reasons are a fault whose fix is named in the manufacturer's release notes, a security advisory that applies to your model, and installing a part the board does not recognise. "Being up to date" is not a reason. Read the release notes for every version between yours and the new one.
- If you do update, do it the safe way.Only from the manufacturer's support page for the exact model and, on a laptop, the exact configuration. Mains power connected and battery above half. Nothing else running. Do not interrupt it, do not close the lid, and expect the machine to restart itself more than once. Reset your firmware settings afterwards if the update clears them.
Common mistakes
- Updating firmware because a driver-updater program said so — Those programs make money by finding things to update. Firmware is the one component where an unnecessary update carries a real risk of destroying the machine, and the manufacturer's own page is the only trustworthy source.
- Turning Secure Boot off to solve something and leaving it off — It is a genuine defence against boot-level malware, and Windows 11 expects it. If a task needed it off, turn it back on when the task is done.
- Changing several settings at once to see what helps — Firmware settings interact, and the machine may not boot to let you undo them. Change one thing, restart, observe. Note what the setting was before you touched it.
If it doesn't work
The setup key does nothing
Cause: Fast startup, or the window is too short to catch — Fix: Go in from Windows instead — Settings, System, Recovery, Restart now under Advanced startup, then Troubleshoot, Advanced options, UEFI Firmware Settings. This route works regardless of timing.
The machine has forgotten the date and its settings
Cause: A flat CMOS battery on the motherboard — Fix: The firmware cannot retain settings without power. On a desktop this is a coin cell and a five-minute job; on a laptop it is usually an internal part. The catalogue's guide on a computer showing the wrong time covers the knock-on effects.
Windows will not install and says the disk is not supported
Cause: A mismatch between the firmware boot mode and the disk's partition style — Fix: UEFI mode expects a GPT disk and legacy mode expects MBR. Setting the firmware to UEFI mode and letting the installer partition the disk resolves most cases.
A firmware update failed partway through
Cause: Interruption, or the wrong file for the model — Fix: Many recent boards have a recovery mode that reads a firmware file from a USB stick with a specific name, and it can save the machine. Check the manufacturer's documentation for BIOS recovery on your model before assuming the board is dead.
The machine is slower or a device stopped working after an update
Cause: The update changed defaults, or included a mitigation with a performance cost — Fix: Firmware settings are often reset to default by an update. Reapply what you had. Most manufacturers publish older versions and allow a rollback, though not always.
A password is set on the firmware and nobody knows it
Cause: A previous owner or a workplace deployment — Fix: On a business laptop this is deliberate and usually cannot be cleared without the manufacturer and proof of ownership. It is a real reason to walk away from a second-hand machine.
Questions people ask
Is BIOS the same as UEFI?
In everyday use, yes — people call the settings screen "the BIOS" whatever it is. Technically BIOS is the older standard and UEFI replaced it, adding a graphical interface, support for drives over 2 TB, faster startup and Secure Boot. Anything bought in the last decade or so is UEFI, often with a compatibility mode for legacy booting.
Can a firmware update fix a slow computer?
Almost never. Slowness is storage, memory, background software or heat. Firmware updates fix compatibility, stability and security problems, and occasionally improve fan behaviour. If someone has told you a firmware update will speed up your machine, be sceptical about the rest of their advice.
What is TPM, and why did Windows 11 ask for it?
A small security chip, or a firmware equivalent, that stores encryption keys — it is what BitLocker uses. Windows 11 requires it, and on many machines that were sold as not compatible it is simply switched off in the firmware and can be turned on. The setting is often called PTT on Intel systems and fTPM on AMD ones.
Should I set a firmware password?
On a laptop that leaves the house it is a reasonable extra layer, because it stops someone booting the machine from their own USB stick. Write it down somewhere you will find it in five years, because on many business machines a forgotten firmware password is genuinely unrecoverable.