Since version 3 DotNetNuke provides a rich set of features to allow static localizability of
modules. By static information we mean all data that is not subject to user modification
and that can be considered for the most part as not changeable. This includes text labels,
error and information messages, help, and graphics that are spread throughout the user
interface of the application.

In DotNetNuke resource files are XML files, used solely for storing translatable and translated texts. Files names are either SharedResources or follow associated .ascx files, extended by ".resx". Extension developers may create resource files using Visual Studio, translators may use the builtin language editor or a 3rd party tool to create resource files. When checking for missing resource files/entries, the ShowMissingKeys entry is useful to highlight additional translations required.

The Localization Guide for DotNetNuke modules contains further useful information on resource files.