Extension:Interwiki

The Interwiki extension adds the "Special:Interwiki" page to MediaWiki, to view and edit the interwiki table, and a log of any actions made with it.

Since Interwiki version 2.1, it works with the $wgInterwikiCache, and the CSS uses ResourceLoader.

The list of "Special:Interwiki" is identical to the API action=query&meta=siteinfo&siprop=interwikimap, except the iw_api field is not available.

Installation

 * The configuration that comes with MediaWiki will not grant permission to any user group. Thus, you will need to add the configuration yourself or no one will be able to edit interwikis.
 * To enable transclusion from other sites, you'll need to enable.
 * To disable adding prefixes through the Special:Interwiki interface, set $wgInterwikiViewOnly to true.

Setting up interlanguage links
To set up interlanguage links using this extension, make sure that $wgInterwikiMagic is set to true and $wgHideInterlanguageLinks is set to false (they are like this by default, you don't need to change them usually). Then go to Special:Interwiki as a user with the appropriate permissions. For example, if the French version of your wiki was located at  http://fr.foowiki.tld/wiki/ , you could add  http://fr.foowiki.tld/wiki/$1  to the interwiki table with values trans 0 and local 0. Then the interlanguage link to the French version would work, but a #REDIRECT to a French-language page from a page in some other language would be refused.

See Manual:Interwiki table for a full explanation of the forward (iw_local) and transclude (iw_trans) bits.

In brief:
 * Enabling forwarding ('local' true) is normally done between all languages and projects in the same group, as it allows a link to any one of the languages to be used as a gateway to the others. The English-language Wikipedia, for instance, sets the 'local' bit true for all of the other-language Wikipedias and for projects like commons:, wikinews: or wikivoyage:. A user on a wiki outside Wikipedia where the wikipedia: interwiki prefix points to en.wikipedia.org could create a link like Encyclopédie. That link goes initially to "fr:Encyclopédie" on the English-language Wikipedia. The en.wikipedia server immediately recognises fr: as a 'local' interwiki link, so replies with a redirect to la Wikipédia where fr.wikipedia.org/wiki/Encyclopédie displays the requested French-language Wikipédia page Encyclopédie et voilà.
 * Enabling transclusion is rarely done, as it allows an article on one wiki to use templates from some other wiki. This is referred to as 'scary transclusion' as it will cause problems if the other wiki changes the template unexpectedly. A few wiki farms use this to create one 'central wiki' with various templates which are made available to other wikis in the same farm. If you don't need this, don't enable it.

Global interwikis
Since version 3, Interwiki supports defining a global/central database and pulling defined interwikis from there as well as from the local table. This functions essentially as a table merge, with local interwiki definitions overriding central. Language links are not pulled from the central table; these are set up as local-only due to a central table likely serving more than one project (with each having its own languages).

The central table is the interwiki table of the central wiki. This means that as far as the central wiki is concerned, it is basically just a normal non-global setup. There are therefore no special rights associated with the central (global) table, though it is likely you may want to be more picky about how you assign the 'interwiki' edit right on this wiki.
 * This was decided by looking at current possible use cases (ShoutWiki's hub, Uncyclomedia's central wiki, and Meta-Wiki) where the central wiki isn't going to have anything extra anyway.
 * This might change in the future, but anything more intelligent will require schema updates.
 * This probably doesn't work with table prefixes because of how the table is accessed.

To set up a central interwiki table, simply provide the name of the database of the wiki you want to use:

Replace 'mw_central' with the name of the database.

For those using table prefixes here is an alternative solution for "pool_example_wiki" tables.

Protocol-relative URLs
MediaWiki supports protocol-relative URLs (PRURLs), from MediaWiki. With a PRURL, a user accessing a page over http or https uses the same scheme to access the interwiki link. To use a PRURL, first ensure the destination server supports HTTPS; if it does, then simply remove the  portion of the URL in the link table. For example, change

http://en.wikipedia.org/wiki/$1

to:

//en.wikipedia.org/wiki/$1