Dead Keys Explained, and Why They Look Broken
Press the circumflex key on a French or German keyboard and nothing appears. Press the letter A straight after it and you get â. The first key was not broken. It was a dead key doing exactly what it was designed to do, and that behaviour is the single most common reason people conclude a working keyboard has a faulty switch.
What a dead key does
A dead key produces no character on its own. It arms a diacritical mark and waits for the next keystroke to decide what to do with it.
- Dead circumflex followed by a gives â, followed by e gives ê, followed by o gives ô.
- Dead acute followed by e gives é, dead grave followed by e gives è.
- Dead diaeresis followed by u gives ü, followed by i gives ï.
Two follow-up cases matter for diagnosis. Pressing space after a dead key prints the bare mark, so circumflex then space gives ^ on its own. Pressing a letter that has no accented form usually prints both characters, so circumflex then s gives ^s. Neither is a fault.
Where dead keys live
On a French AZERTY layout the circumflex and diaeresis share one key to the right of P. Plain press arms the circumflex, Shift arms the diaeresis, which covers every accented vowel French needs beyond é, è and ç.
On a German QWERTZ layout there are two. The caret key at the far top left of the board, left of the digit 1, arms a circumflex. The key to the right of ß arms an acute on a plain press and a grave with Shift. German text needs those marks rarely, which is why many German typists never notice the keys are dead until they try to type a lone accent.
Polish takes the opposite route: the programmer layout most Polish users run has no dead keys at all, because every accented letter is reached by holding AltGr, and this is precisely why it behaves so predictably.
Why a key test can make a dead key look faulty
Browsers report two separate things about every keystroke. The physical position of the key is reported as a code, such as Backquote or BracketRight, and it arrives the moment the switch closes. The character is reported separately, and for a dead key the browser reports the literal value Dead instead of a letter.
So a page that only watches characters sees nothing useful and appears to ignore the key. A page that watches physical positions registers the press immediately and highlights the correct cell. Keys&Type reads the physical position first and the character second, which is why a dead key lights up here even though a text field would stay empty.
The role of AltGr
AltGr is the right Alt key on almost every layout outside the United States, and it opens a third level of characters on keys that already carry two. On a German board it produces @ from Q, € from E and the curly braces from 7, 8, 9 and 0. On a Polish programmer layout it produces ą, ć, ę, ł, ń, ó, ś, ź and ż from the matching base letters.
AltGr also produces dead keys of its own on several layouts, and it is not the same as left Alt. On Windows it behaves as Ctrl plus Alt held together, which is why holding left Ctrl and left Alt can substitute for it, and also why some old software fires an unwanted shortcut when you reach for a brace.
US against US International
The plain US layout has no dead keys whatsoever. Every key prints immediately, and accented letters are unavailable without a character picker.
The United States International layout keeps the same physical positions and turns five punctuation keys into dead keys: apostrophe, quotation mark, grave, tilde and circumflex. The gain is that é, ñ, ü and ô become two-keystroke sequences. The cost catches everyone at least once. Typing an apostrophe inside a contraction now waits for the next letter, so don't comes out as doń unless you press space after the apostrophe or use the variant that keeps punctuation live.
Anyone who suddenly finds their apostrophes and quotation marks misbehaving has almost certainly been switched to this layout, often by an accidental Windows shortcut rather than a deliberate choice.
How to diagnose a suspect key
1. Press the suspect key in the keyboard test. If its cell highlights, the switch and the cable are fine, and the behaviour you are chasing belongs to the layout. 2. Press the key and then space. A bare accent mark proves it is a dead key. 3. Check which layout the operating system has active, and compare the character produced against the layout you believe you are using. 4. If the cell does not highlight at all, the problem is genuinely the key. Clean it, then retest. A dead key stays silent in a text box but never silent in a physical key test.