German Alphabet: ä, ö, ü, ß and When ae, oe, ue, ss Stand In

Are ä, ö, ü and ß letters of the German alphabet, or extras?

Ä, ö, ü and ß are full letters of the German alphabet. The Amtliches Regelwerk (opens in a new tab), the official spelling rules of the Rat für deutsche Rechtschreibung, opens with the alphabet as a list. It writes a to z, then ä, ö, ü and ß. Under them it writes the capitals, and the last one is ẞ. The rule above the list says that every letter exists as a small and a capital letter.

The same page says how the extra letters behave. The umlaut letters are filed with a, o and u. The ß is filed after ss. Letters with other marks, such as ç, é and â, and ligatures such as œ, turn up only in foreign words and foreign names. Such letters fill the CLDR list further down the page.

Letters	Status in the Regelwerk	Filed in its word list
a to z, with A to Z	the basic letters	in their own order
ä, ö, ü, with Ä, Ö, Ü	umlaut letters	with a, o and u
ß, with ẞ	a letter; the capital was allowed in 2017	after ss
ç, é, â, œ and others	met in foreign words and names only	not covered by the list

The ẞ row is recent. The Council's press release of 29 June 2017 (opens in a new tab) allowed the capital beside SS. It gave the reason too: names in passports and ID cards. The grid at the top shows ß without a capital for another reason. Unicode's default uppercase of ß is SS, and the CLDR data behind the grid follows Unicode.

So the size of the German alphabet depends on what you count. The grid above follows CLDR and the Regelwerk: the umlaut letters and ß are letters like the rest. They never open a section of their own in a dictionary, though.

How do you say German letter names and spell ä, ö, ü and ß out loud?

Most letter names in the German alphabet are the sound plus a vowel: A, Be, Ce, De, and so on to Zett. A handful surprise English speakers. Wiktionary's list of German letter names (opens in a new tab) gives the full set. The sounds below are from its entries for Jot (opens in a new tab), Vau (opens in a new tab), Ypsilon (opens in a new tab), Zett (opens in a new tab) and Eszett (opens in a new tab).

Letter	German name	Said	The trap for an English ear
J	Jot	/jɔt/	starts with the sound of English y
V	Vau	/faʊ̯/	sounds like English f, plus ow
Y	Ypsilon	/ˈʏpsilɔn/	three syllables, from the Greek letter
Z	Zett	/t͡sɛt/	starts with ts, not z
ß	Eszett	/ʔɛsˈt͡sɛt/	Es plus Zett, after its old ligature of long s and z

Spelling a name on the phone needs more than letter names, because they blur on a bad line. DIN gives its own example: it chose Goslar over Gera for G, since Gera can be misheard as Jena.

Germany has a standard word list for that, in DIN 5009. Its 2022 edition, DIN 5009:2022-06 (opens in a new tab), swapped the old first names for city names. DIN's own questions and answers (opens in a new tab) give the reason. The table had been stripped of Jewish first names in 1934, and the post-war fix was never complete.

What you spell	The DIN 5009 rule of 2022
Ä, Ö, Ü	the word Umlaut, then the city for the base letter: Umlaut Aachen, Umlaut Offenbach
ß	Eszett, its own name, since no city fits
Y	Ypsilon, its own name
CH, SCH	no word of their own any more; spell the letters one by one

So Müller on the phone starts with the M city and then Umlaut and the U city. DIN also explains why it did not adopt the ICAO alphabet, the one with Quebec and Zulu. That list has no word for the umlaut letters or for ß.

When may German write ae, oe, ue and ss instead of ä, ö, ü and ß?

Of the four stand-ins, only ss has a rule in German spelling itself. § 25 E2 of the Regelwerk says to write ss where ß is not available. In Switzerland and Liechtenstein ss may always be written. For ä, ö and ü the Regelwerk gives no stand-in at all. The ae, oe and ue habit comes from other rule books, and the passport is the main one.

Where the letter goes	ä, ö, ü	ß	Who says so
ordinary German text	no stand-in in the rules	ss, when ß is not available	Regelwerk § 25 E2
text set in capitals	Ä, Ö, Ü	ẞ or SS: STRAẞE, STRASSE	Regelwerk § 25 E3
a person's or a place's name	the official spelling of the name	the official spelling	Regelwerk, preface (3.2)
passport, printed name	as spelled; ẞ is allowed	as spelled	ICAO Doc 9303, Part 3, 3.1
passport, machine-readable line	AE or A, OE or O, UE or UXX or U	SS for ẞ	ICAO Doc 9303, Part 3, 6.A
German public-sector software	must handle every Latin letter of DIN 91379	the same	IT-Planungsrat, by 1 November 2024

The passport rows come from ICAO Doc 9303 (opens in a new tab). Under its table, Müller can appear in the machine line as MUELLER, MUXXLLER or MULLER. The last row comes from the IT-Planungsrat (opens in a new tab), the federal and state IT council. It set 1 November 2024 for public IT systems to conform to DIN 91379 (opens in a new tab), the standard list of Latin characters for names. The decision was aimed at names with letters that are rare in German, which older systems often mangled.

The stand-in matters most in search. We tested it on 2026-10-13 in Node.js v26.0.0, which runs ICU 78.3 on CLDR 48. We compared at the strength that ignores case and marks. Under German rules, a search for Mueller found Müller and a search for Muller did not. Under English rules it was the other way round. Write ue, not u, when the dots are missing. Better still, type the dots: the German keyboard page types ä, ö, ü and ß and copies them.

Outside Germany the stand-in can become the name. Wiktionary's English entry for Mueller (opens in a new tab) calls it a surname from German Müller (opens in a new tab). It is said /ˈmʌlɚ/ or /ˈmjuːlɚ/, as the bearer prefers. In German, Müller is /ˈmʏlɐ/.

Why is the oe in Soest not an ö?

Because the e in Soest is not an umlaut. Wiktionary's entry for Soest (opens in a new tab) says the e marks a long vowel and gives the town as /zoːst/: a long o, no ö. The Regelwerk itself names Duisburg and Soest among the names that break the regular match of letters and sounds. Schmidt and Schmid, and Maier, Meyer and Meier, are its other examples.

Several German place names write a long vowel this way. To a script, their letters look like stand-ins for the umlaut letters of the German alphabet. Each pronunciation below is Wiktionary's, from its entries for Coesfeld (opens in a new tab), Itzehoe (opens in a new tab), Straelen (opens in a new tab), Raesfeld (opens in a new tab), Kevelaer (opens in a new tab), Duisburg (opens in a new tab) and Troisdorf (opens in a new tab).

Name	Letters that look like a stand-in	Said	What they spell
Soest	oe	/zoːst/	long o
Coesfeld	oe	/ˈkoːsfɛlt/	long o
Itzehoe	oe	/ɪt͡səˈhoː/	long o
Straelen	ae	/ˈʃtʁaːlən/	long a
Raesfeld	ae	/ˈʁaːsfɛlt/	long a
Kevelaer	ae	/ˈkeːvəˌlaːr/	long a
Duisburg	ui	/ˈdyːsbʊrk/	the sound of ü, without dots
Troisdorf	oi	/ˈtʁoːsdɔʁf/	long o

A script that turns every oe back into ö writes Söst and Cösfeld. One that turns ae into ä writes Strälen and Räsfeld. Both are wrong, and neither is easy to catch.

In the same test, German search rules treated Soest and Söst as equal, because they read ö as oe. A search will find the town under the wrong spelling and hide the mistake. Fix names against a list of real names, never by a blanket swap.

How do German dictionaries and phone books sort ä, ö and ü?

The German alphabet has two standard orders. A dictionary files Bär next to Bar, as the Regelwerk does. A phone book files Bär as if it were Baer. Germany's filing standard is DIN 5007-1 (opens in a new tab), "Ordnen von Schriftzeichenfolgen", the ABC rules of 2005. Its text is not free to read, so this page shows the two orders as software encodes them.

The CLDR German collation chart (opens in a new tab) has both. In its rules file (opens in a new tab), the standard German order is the same as the root order, where ä is an a with a minor difference. The phone-book order adds one line per letter, such as &AE<<ä: sort ä as ae.

Windows has the same choice under the name de-DE_phoneb, German phone book order, in Microsoft's list of sort orders (opens in a new tab). We sorted four sets of names under each order on 2026-10-13, in the Node.js build named above.

Names sorted	German dictionary order	German phone-book order
Mumm, Müller, Muller, Mueller	Mueller, Muller, Müller, Mumm	Mueller, Müller, Muller, Mumm
Goethe, Göbel, Goebel, Gobel	Gobel, Göbel, Goebel, Goethe	Gobel, Goebel, Göbel, Goethe
Bär, Baer, Bar, Bart	Baer, Bar, Bär, Bart	Baer, Bär, Bar, Bart
Kühn, Kuehn, Kuhn, Kuhl	Kuehn, Kuhl, Kuhn, Kühn	Kuehn, Kühn, Kuhl, Kuhn

The control is English. English rules gave the dictionary column in every row, since they too read ü as a u with a mark. Only the phone-book order moves the umlaut names, and it puts each one next to its ae, oe or ue spelling. That is the point of it. A caller who heard Kühn and looked under Kuehn finds the two next to each other.

Are the dots in Citroën a German umlaut?

No. In the German alphabet, the two dots are an umlaut only on a, o and u. On any other letter they are a diaeresis, the mark that splits two vowels, and they come with a foreign name such as Citroën (opens in a new tab).

The CLDR rules file states the line in a note on the European ordering standard, EN 13710. It treats the umlaut as distinct from the trema, the diaeresis, and allows it only on a, o and u.

Two dots on	What they are in German text	The stand-in without them
a, o, u: ä, ö, ü	umlaut letters of the alphabet	ae, oe, ue
e, i: ë, ï, as in Citroën	a diaeresis in a foreign name	e, i; ICAO gives Ë as E and Ï as I

The test above confirms the split. German search rules matched Citroen with Citroën but not Citroeen. The ue rule covers only the three umlaut letters, so Citroën never becomes Citroeen. Where the two dots come from, and what they do in other languages, is on the umlaut and diaeresis page. Wiktionary's entry for Umlaut (opens in a new tab) adds the one German combination the dots also mark: äu, as in the Regelwerk's own example Räuber, from rauben.