Keyboard keys not working or typing twice: how to find out why

“My keyboard is broken” covers at least four different faults, and they do not share a fix. Cleaning cures one, a settings change cures another, and one means a new switch. Two minutes of testing tells you which you have.

First, find out what the keyboard is actually sending

Open the keyboard test, choose the layout you own (ANSI, ISO, Mac, laptop or 60%), and press every key once. Each key that reaches the browser turns green. What you are left with falls into one of these:

What you see	The fault	Likely cause
A key never lights	Dead key	Failed switch, cable or wireless link, driver
A key turns red	Chatter: one press, two signals	Worn or dirty switch
A key turns amber with hands off	Stuck key	Debris under the cap, a sticky spill
Keys light alone but drop out together	Ghosting	The keyboard’s rollover limit
Everything lights, one app ignores a key	Software	That app’s shortcuts or a remapping tool

Keys drawn with a dashed outline, such as Fn, media and brightness keys, never reach a web page. Leave them out of the verdict.

A key that does nothing

If a whole row or block is dead, suspect the connection before the keys:

1. Wired: try another USB port, directly on the computer rather than a hub.
2. Wireless: replace or charge the batteries, move the receiver to a front port, re-pair it.
3. Laptop: restart. If the keys work in the firmware or login screen but not after, it is a driver or a setting such as Filter Keys on Windows.

If single keys are dead and scattered, it is the switches. On a mechanical board a single switch can be replaced. On a laptop, a dead key usually means a new keyboard assembly, which is worth knowing before the warranty ends.

A key that types twice

Double letters that come and go are chatter, and the difficulty is proving it, because it is intermittent. On the Chatter tab, tap the suspect key about forty times, slowly, one deliberate press at a time. The test flags any press that follows a release faster than a finger can move: a person cannot release and re-press a key within 50 milliseconds, and a bouncing switch does.

What helps, in order of effort:

• Compressed air under the cap, with the board upside down.
• Reseating the keycap, and on a hot-swap board, the switch.
• A longer debounce time, if your keyboard’s software offers one. It hides the bounce without removing the cause.
• A new switch. Worn contacts do not recover.

A key that repeats or holds itself down

Take your hands off the keyboard and watch the layout. A key held for more than three seconds turns amber and is counted as stuck. The usual cause is something under the cap: crumbs, or the residue of a drink. Pull the cap, clean around the stem with a little isopropyl alcohol on a cotton bud, and let it dry.

If no key shows as stuck but letters still repeat while you type, check the operating system’s key-repeat delay, which may simply be set very short.

Keys that fail only together

Hold down keys one at a time on the Rollover tab and watch the count. The page shows the most it saw at once. Six or more is enough for almost every game. Three to five means some combinations will be dropped, which is a property of the keyboard and not something that can be repaired. The browser shows a floor, so the keyboard’s true limit may be higher than the number you see. The keyboard ghosting test guide explains which combinations to try and what the rollover labels mean.

If you are returning it

Press Copy summary. It gives a dated, plain-text list of the keys that were never pressed, the ones that chattered and the ones that stuck. Paste it into the support ticket. It reads better than “some keys are acting up”, and it is the evidence a warranty desk asks for.

While you are at it

A keyboard fault on a used laptop often travels with others. The same two minutes will cover the mouse or trackpad, and there is a guide to checking the screen before a return window closes.