Hi, I checked the German index sorting rules, and as far as I can tell, all of them are somewhat wrong. – de, default, or no setting (just mainlanguage de) – Duden - DIN 5007-1(:2005) - DIN 5007-2(:1996) - de-AT IMO, "Duden" is obsolete, should be the same as default; it makes no sense to have a default setting that doesn’t adhere to the official rules. If Û#m not mistaken it’s also the same as DIN 5007-1; maybe there was a difference before 2005. (DIN 5007-2 and de-AT have their uses.) The order of umlauts etc. should be ok. [ß] In tex/context/base/mkiv/sort-lan.lua, ß is replaced by s, while it should be sorted like ss in default and both DIN versions. (de-AT sorts ss after ß.) [upper-/lowercase] While casing is not mentioned in Wikipedia (https://de.wikipedia.org/wiki/Alphabetische_Sortierung), Duden „Satz und Korrektur“ says: Uppercase characters get sorted the same as lowercase (i.e. mixed), but if both appear, lowercase comes first. ATM all German settings sort lowercase behind uppercase. Generally, default method seems to be not "default" but "before". Does this make sense? If we look at the method presets, there’s none for {zm,pm,zc,zm,uc} (upper like lower, ignore diacritics – basic default for German). """ \mainlanguage[de] \setupregister[index][language=de] \starttext \index{Apfel} \index{Äpfel} \index{apfel} \index{äpfel} \index{aepfel} \index{Aepfel} \index{Ápfel} \index{ápfel} \page \completeindex \stoptext """ default order should be: aepfel Aepfel apfel Apfel äpfel Äpfel ápfel Ápfel aqua DIN 5007-2 sorts like: aepfel Aepfel äpfel Äpfel apfel Apfel ápfel Ápfel aqua de-AT sorts like: aepfel Aepfel apfel Apfel aqua äpfel Äpfel ápfel Ápfel Hraban