User blog comment:The Kaufman/A random proposition/@comment-24425594-20150123191016/@comment-25438171-20150124220356

One cannot strictly make a template wikiwide. However, it isn't too hard to cover quite a large number of pages.If one adds the template to the top of the following pages:

Mediawiki:Welcome-message-user

Mediawiki:Welcome-user-page

Template:NewLang

then that covers a number of the pages that will be created on the wiki. It is then simply a matter of requesting current users to add the template to the top of their user page, talk page and any languages they come across (including all their own). It isn't wikiwide, certainly, but most pages across which a browser would come display the template.

P.S. @Kaufman, would you want the template added to the top of the homepage?