Manual:$wgCategoryCollation/en

Details
The setting determines what collation algorithm should be used to sort category listings. See also.

Currently supports:


 * [default]: make everything uppercase, then sort by binary value of string when stored as UTF-8. Essentially case-insensitive sort by code point.
 * [MW 1.28+]: Same as, but with numeric sorting.
 * [MW 1.18+]: sort by binary value of string when stored as UTF-8 (without converting to uppercase). Essentially sort by code point.
 * [MW 1.17+]: Unicode collation algorithm – complex, much more multilingual-friendly category collation.
 * [MW 1.28+]:  with numeric sorting.
 * [MW 1.21+]:  with language-specific adjustments, see below.
 * [MW 1.28+]:  with numeric sorting.

Since MediaWiki 1.18, extensions can add extra collations via the hook.

The value is also stored inside the categorylinks table to determine which rows need updating when the collation algorithm changes.

Language-specific collations
MediaWiki also supports 70 collations designed for specific languages. These are based on  and have the same requirements; they are named , where is one of: af, ast, az, be, be-tarask, bg, br, bs, ca, co, cs, cy, da, de, dsb, el, en, eo, es, et, eu, fa, fi, fo, fr, fur, fy, ga, gd, gl, hr, hsb, hu, is, it, kk, kl, ku, ky, la, lb, lt, lv, mk, mo, mt, nl, no, oc, pl, pt, rm, ro, ru, rup, sco, sk, sl, smn, sq, sr, sv, ta, tk, tl, tr, tt, uk, uz, vi

For example, to use a collation for Spanish, one would use the  collation.

Using these collations provides both correct sorting order for given language and proper headings for first letters of article titles.

Getting new collations added
There are two parts to having a new language supported:


 * It being supported by the ICU library (the list of language codes it supports is available at ). Note, however, that Wikimedia's production servers do not use the latest version of the ICU library. As of 2016, they use version 52.1, which supports a significantly smaller set of languages.
 * It being additionally supported by MediaWiki itself (this basically requires listing the additional characters, or character groups, that are considered separate letters in the given language, in addition to the basic alphabet) – the always up-to-date list of currently supported ones is available at ).

It might also be the case that the default ICU ordering ('uca-default' collation) orders the titles correctly, but does not correctly separate the letters – it can be used for the first step in that case. Sometimes the letter ordering of a different language might fit yours, if they are related – a custom collation can sometimes be provided in such case (there is one for Sorani Kurdish / Central Kurdish language ('ckb') already, called  ).

Numeric sorting
Under numeric sorting, pages will be sorted as such: 1, 2, 9, 10, 11, 20, 21, 99, 100. Under regular (non-numeric) sorting, pages will be sorted as such: 1, 10, 100, 11, 2, 20, 21, 9, 99. If numeric sorting is used, all pages starting with a number will be sorted together under a single header: "0–9". If regular sorting is used, pages starting with a number will be sorted under separate headers for whichever number each title begins with: "0", "1", "2", etc. For more information about numeric sorting, see the Unicode Technical Standard #10. To test numeric sorting, see the ICU Collation Demo. Note that numeric sorting only works for unbroken sequences of digits. Digits separated by commas, periods, or spaces are treated as separate numbers.