Aide:Interwiki linking

General

By adding a prefix to another project, internal link style ("prefixed internal link style") can be used to link to a page of another project. A project's own namespace prefix can not be reused as code for an external project. However, the prefix used for a target project may coincide with the prefix for a project namespace within that project. As a result, to link to a page in that namespace, use the same prefix twice, e.g. [[en:Wikisource:Wikisource:Scriptorium]].

For portability across projects, one may want to select a link code that leads to the same target from all projects, e.g. MetaWikipedia:wikibooks:Main Page. The "superfluous" "MetaWikipedia:" prevents "wikibooks:" to be interpreted as namespace prefix when the code is used at wikibooks itself, while at Meta the "MetaWikipedia:" is ignored (it is not a namespace prefix, and even at Meta itself it is recognized as code for Meta). The codes above work from all projects. However, the existence detection and the self-link feature do not work on interwiki links.