# Index configuration

The common/index folder houses custom index definition files that override the standard definitions in org.dita.pdf2/cfg/common/index.

Each file contains data for a single language, and should take that language’s ISO 639-1 language designator as its name (for example, pt.xml for Portuguese). If necessary, locale-specific customizations can be provided by adding a region designator to the file name (for example, pt_BR.xml for Brazilian Portuguese).

The index files consist of `<index.group>` elements which contain sorting information on one or more characters. Index groups are listed in sort order (“specials” before numbers, numbers before the letter ‘A‘, etc), and the `<char.set>` entries they contain are also listed in sort order (uppercase before lowercase).

The best way to start editing a custom index file is by making a copy of the original from org.dita.pdf2/cfg/common/index and making changes as desired.

In order to apply a custom index definition to your publishing outputs, edit catalog.xml and uncomment the appropriate entry in the “Index configuration override entries” section.