How to type U with Diaeresis

ü lives in the Latin-1 Supplement block (U+0080-U+00FF), the accented letters and common signs Western European languages needed. Within Unicode it is classified as Ll, a lowercase letter. It has an uppercase counterpart and changes under case conversion. Its bidirectional class makes it left-to-right.

ü has a decomposed form: it can also be written as U+0075 Latin Small Letter U, U+0308 Combining Diaeresis. The two look identical and are not equal as strings, which is why a search for a word containing ü sometimes fails against text that was typed on a different system. Everything on this site uses the single-codepoint (NFC) form shown here.

Its uppercase counterpart is Ü (U+00DC). They are separate codepoints, so a byte comparison treats them as different characters even though a case-insensitive search does not.

Typing ü without switching keyboard

ü is the letter U carrying a diaeresis, and it is needed in French, Spanish and German. It is one character rather than two: a spell checker treats it as a letter of those alphabets, not as U with something added.

Both of the routes worth knowing compose the letter rather than looking it up. On a Mac press Option + U, let go, then press u: nothing appears until the second key, because the first one is a dead key waiting for a letter to sit under. On Windows the same idea needs the United States-International layout, which turns Shift + apostrophe into the same dead key. Add that layout once under Language and region, and ü costs two keystrokes from then on rather than four digits on a numeric keypad.

How U with Diaeresis behaves in software

ü is East Asian Ambiguous: one column in a Western locale and two in a CJK one. That is why a table that lines up on your machine can break on somebody else's, with no change to the text at all. It is a left-to-right character, so it holds that direction even inside a right-to-left paragraph.

Every way to write U with Diaeresis

If ü arrives as ü

That is this exact character, undamaged: its two UTF-8 bytes C3 BC are being read one at a time as Windows-1252. The Latin-1 range is where this happens most, because it is the range every legacy system thought it already handled. Nothing is lost, and retyping will not help: the fix is at the reading end, which has to be told the text is UTF-8. An empty rectangle is the opposite complaint, and means the encoding is right and the font has no glyph for U+00FC.