Although not a part of their alphabet, Ü also appears in languages such as Finnish and Swedish when retained in foreign proper names like München ("Munich").

In other languages that do not have the letter as part of the regular alphabet or in limited character sets such as ASCII, U-umlaut is frequently replaced with the two-letter combination "ue".

This same letter appears in the Chinese Romanisations Pinyin, Wade–Giles, and the German-based Lessing-Othmer, where it represents the same sound [y]: 綠/lǜ (green) or 女/nǚ (female).

Catalan also uses the letter ü to indicate that a vowel pair that would normally form a diphthong must be pronounced as separate syllables (e.g. baül, diürna).

Similarly, in Spanish, ü is used in the combinations güe [ɡwe] and güi [ɡwi], to distinguish them from "gue" [ɡe] and "gui" [ɡi] (e.g. nicaragüense, pingüinos).

Unlike Catalan, though, Spanish does not use it after q, instead using cue and cui to spell words with [kwe] or [kwi] sounds (cuestión, acuicultura); it also does not use it to break diphthongs, sometimes using the letter ú for that purpose when necessary (baúl, but diurna).

After the 1990 spelling reforms, it is applied to a few more words, like aigüe (formerly aiguë), ambigüe (formerly ambiguë) and argüer [aʁɡɥe] (formerly without the diaeresis).

In the Rheinische Dokumenta, a phonetic alphabet for many West Central German, Low Rhenish, and related vernacular languages, "ü" represents a range from [y] to [ʏ].

In modern typography there was insufficient space on typewriters and later computer keyboards to allow for both a U-with-dots (also representing Ü) and a U-with-bars.