Step 1 — Prove the key is actually dead

Open the tester, tap it once to arm it, and press the suspect key. Three outcomes:

• Lights and shows the right key — the key works; the problem is in the app where it “doesn’t work.” Skip to step 2.
• Lights but shows the wrong key — hardware fine, layout wrong. Step 3.
• Doesn’t light at all — no event reached the browser. Continue with steps 4–7.

Step 2 — Check the obvious software causes

• Try the key in a plain text field (address bar, notepad). If it works there, the app that ignores it has a binding or focus issue — check its keyboard shortcut settings.
• Look for remapping layers: PowerToys Keyboard Manager (Windows), Karabiner (macOS), keyd/udev rules (Linux), gaming-software profiles (Razer Synapse, Logitech G HUB, iCUE). A “dead” key is very often a remapped-to-nothing key.
• Check accessibility features: Filter Keys on Windows ignores brief or repeated presses; Sticky Keys changes modifier behavior. Both get toggled by accident.
• Close overlays — screen recorders, RGB tools, macro suites — that hook the keyboard.

Step 3 — Wrong character? It’s the layout

The readout’s key field shows the character the OS produced. If you press Y and see z, or @ and " swap places, the OS is using a different layout than the keycaps assume — fix it in language/keyboard settings, not the hardware. Laptop owners docking to external boards hit this constantly.

Step 4 — Rule out the computer

Plug the keyboard into another machine, or boot a live Linux USB. A key dead on two computers is hardware; a key dead on one is the OS or a port. Also try a different USB port — preferably a rear motherboard port on a desktop, skipping hubs and front-panel headers, which are common failure points for power-hungry boards.

Step 5 — Look at the switch

Pull the keycap (a wire puller or careful fingernail) and look for debris — hair, crumbs, dried liquid. Compressed air at an angle, a soft brush, or a cotton swab barely damp with isopropyl alcohol fixes more “dead” keys than any other single step. Press the bare switch stem directly: if it registers reliably without the cap, the cap itself was interfering.

Step 6 — Interpret the failure pattern

• One key dead, others fine — failed switch or a dead spot on the matrix. Mechanical: replace the switch (trivial on hot-swap, soldering otherwise). Membrane/laptop: see the laptop checklist — usually a sheet replacement.
• A cluster or row of keys dead — matrix line or ribbon cable. On laptops, often a connector that worked loose after a bump or a repair.
• Intermittent — dirty contact, failing solder joint, or a cable flexing. Note when it fails (after moving the board? when warm?) — that pattern is the diagnosis.
• Double presses — switch chatter, see the FAQ above.

Step 7 — Decide repair vs. replace

Hot-swap mechanical: buy the switch, done in minutes. Soldered mechanical: worth it if you own an iron. Membrane desktop board: replacement keyboards cost less than the repair time, unless it’s a model you love. Laptop: the laptop keyboard fix checklist covers ribbon reseating and when a top-case or palm-rest assembly is the real answer.

Frequently asked questions

How do I know if a dead key is a software or hardware problem?

Test the key somewhere neutral — this page's tester, a different app, or better, a different computer or a live USB OS. If the key fails everywhere on every machine, it's hardware. If it works in one app but not another, or produces a wrong character, it's software: a layout mismatch, a remapping tool, or an app binding that swallows the keystroke.

The key lights in the tester but types nothing — what's wrong?

The hardware is fine — the key event reaches the OS. The problem is downstream: the focused app isn't accepting input, an input method or remapper is eating the event, or your keyboard layout translates the key to something invisible (a dead key / accent-composition key on international layouts). Check the tester's key readout — if it shows a different character than the cap says, it's a layout issue.

Can a dead key be fixed without replacing the keyboard?

Often. Crumbs and dust under the cap are the most common cause and a cap pull plus compressed air fixes them. On a hot-swappable mechanical board, a dead switch is a two-minute swap. On a soldered board it's a soldering job. On a membrane or laptop keyboard, a truly dead contact usually means replacing the membrane sheet or the keyboard itself — but rule out every software cause first, because those are free.

Why did several keys die at once?

Multiple simultaneous failures usually aren't failed switches — they're a broken matrix row or column line, a damaged ribbon cable or connector, or a spill that corroded a trace. The failed keys often sit on the same electrical row even when they're not adjacent on the board. Liquid damage is the prime suspect if it followed a spill.

My key double-types or misses presses but isn't fully dead — same thing?

Different fault. Double-registration is switch chatter — the contacts bounce longer than the firmware's debounce window — common on aging mechanical switches; some boards let you raise the debounce time in firmware, and cleaning sometimes helps. Missed presses that come and go are often a dirty contact or a switch on its way out. Both are hardware faults the tester can show: watch for a key that lights twice on one press, or fails to light intermittently.