Step one: map exactly which keys are dead
When a few keys stop responding, resist the urge to guess and take a full inventory instead. Typing into a text editor won't tell you anything about arrow keys, function keys or modifiers, since they don't print a character, and after thirty keys you will have lost track of which ones you already tried.
Open our keyboard test and press every key once, working from Esc in the top-left corner to the bottom-right. The on-screen virtual keyboard lights up each key as you press it, keeps it marked as tested afterwards, and counts the tested keys as you go. Anything that never lit up by the end is a dead key. The test runs entirely in your browser and nothing you type is uploaded anywhere.
Write the dead keys down or take a screenshot. Whether it is a single key, a group of neighbours, or a scattered handful changes the diagnosis completely, so this map is the evidence everything else rests on. Make a separate note of keys that only register when you press unusually hard, because that is a slightly different fault from a key that never registers at all.
Reading the pattern: one key, a cluster, or everything
One dead key, or two unrelated ones, almost always means the fault is local to that key. On a mechanical keyboard that is a worn or contaminated switch; on a membrane or laptop keyboard it is usually crumbs or hair under the keycap, or a damaged rubber dome. Keys that need a hard press belong in this category as well.
Several keys dying together points to the circuit rather than the keys. Keyboards are wired as a matrix of rows and columns instead of one wire per key, and the electrical rows rarely match the visible ones. When a single trace fails, you lose a set of keys that looks oddly arbitrary: a rough diagonal, a few keys stacked vertically, or a group spread across the board. This is the classic aftermath of a liquid spill on a laptop, often showing up days later as the residue corrodes the membrane traces or the contacts of the ribbon cable that links the keyboard to the motherboard.
If every key is dead at once, stop thinking about keys and look at the connection. Check the USB cable and port, a flat battery or lost pairing on a wireless keyboard, and only then the driver. Moving to a different USB port, or charging and re-pairing a wireless board, fixes a surprising share of these cases.
Rule out settings and software before blaming hardware
Windows accessibility features are the most common false alarm. Filter Keys tells Windows to ignore brief keystrokes, which feels exactly like a failing keyboard, and Sticky Keys changes how modifiers behave. Filter Keys can be switched on by holding the right Shift key for eight seconds, so plenty of people enable it without realising. Open Settings, go to Accessibility, then Keyboard, and make sure both are off.
When a specific block of keys is affected, suspect a lock state. A numeric keypad that does nothing usually means NumLock is off. Function keys that only change brightness and volume mean Fn lock is engaged. Many gaming keyboards also have a game mode that deliberately disables the Windows key so you cannot tab out by accident, and it is easy to forget it is on.
If keys respond but produce the wrong characters, the culprit is the keyboard layout or input method rather than the hardware. Check that the input language has not switched to a different layout, and that your IME is set correctly if you type in a language that uses one. Remapping utilities and vendor software profiles can also disable or reassign individual keys, so quit them and test again. Here is a useful rule of thumb: if a key lights up in our test but does nothing in another program, the keyboard is fine and the problem is in software.
Separating an operating system problem from a hardware one
The cleanest check is to try the key somewhere the operating system is not involved. Restart the computer, enter the BIOS or UEFI setup screen, and navigate the menus with the arrow keys or whichever keys are misbehaving. No drivers or background apps are loaded at that point. A key that fails there is a hardware fault, full stop. A key that works there but not in Windows sends you back to settings and drivers.
The second check is a swap. With a desktop keyboard, plug it into another computer and run our keyboard test again to see whether the same keys stay dark. With a laptop, connect an external USB keyboard. If the same keys work fine on the external board, the operating system is healthy and the built-in keyboard hardware is at fault.
If you do suspect the driver, uninstall the keyboard in Device Manager and reboot so Windows reinstalls it automatically. Keep expectations modest, though. Driver faults normally take out the whole keyboard, and it is rare for a driver to be the reason three particular keys stopped working.
Hardware fixes you can try yourself
A single dead key often comes back after cleaning. Unplug the keyboard or power down first. On boards with removable keycaps, pull the cap straight up with a keycap puller and clear out whatever is underneath. Use compressed air in short bursts with the can held upright, otherwise it can spit liquid propellant. Laptop keycaps sit on thin plastic clips that differ from model to model and snap easily, so look up the procedure for your exact model before prying anything.
After a spill, cut the power immediately, disconnect the cable or battery, and leave the keyboard upside down to drain and dry. Sugary drinks leave a sticky film that blocks contacts as it dries. High-concentration isopropyl alcohol on a cotton swab dissolves that residue and evaporates quickly, which plain water does not. Do not power the keyboard back on until it is completely dry.
On a hot-swappable mechanical keyboard, simply reseating the switch can do the trick. Pull it, check that the two metal pins are straight, and push it back in vertically. You can also swap it with a working switch from another position. If the fault follows the switch, replace the switch. If the same position stays dead with a known-good switch, the socket or the circuit board is the problem.
For a cluster of dead keys on a laptop, reseating the keyboard ribbon cable is the last thing worth trying, and it is an advanced step. It involves opening the bottom cover, disconnecting the battery first, flipping up the tiny latch on the keyboard connector, sliding the cable out and fully back in, and locking it again. Those latches are fragile. If the laptop is under warranty or you have never opened one, leave this to a service centre.
Repair or replace?
Under warranty, use it. A screenshot of our virtual keyboard with the dead keys left unlit makes the fault easy to explain to support. Be aware that liquid damage is excluded from most warranties, so ask for a paid repair quote before you commit.
For a desktop membrane keyboard with a damaged circuit sheet, repair usually costs more than a replacement, so buying a new one is the sensible call. Mechanical keyboards are far more repairable because the fault is normally confined to individual switches. A hot-swap board needs one new switch and thirty seconds, and even soldered switches are a routine job for a repair shop.
Laptops are typically fixed by replacing the whole keyboard module, and on models where the keyboard is part of the top case the bill climbs quickly. If the quote is hard to justify, using an external keyboard is a perfectly reasonable long-term answer. Finally, make sure you are solving the right problem. Keys that register intermittently or type double letters are covered in our key chatter guide, and keys that drop only when several are held together are usually a rollover limit, which our keyboard rollover (NKRO) guide explains.