This is a page dedicated to collecting all the loading indicators within the Wikimedia projects. These loading indicators are grouped into purposes such as loading indicators to indicate "content loading" and "tool loading." If you see more around, feel free to add to this page and group them accordingly. This associated task on Phabricator, where you can discuss this topic with us.

User:Splarka has done some analysis here that is also useful on how loaders will work on different colored backgrounds.

Indeterminate

Intentions:

Gives users an idea that a button has been pushed and request has been executed
Gives users an idea that e.g. a page is loading

Content loading

Echo - loading notifications (OOUI PendingElement mixin)
Content translation - loading article
Flow - loading more topics
Mobile - loading nearby articles
Translate on Mediawiki - loading content

Tool loading

Wikimedia Commons - loading upload wizard

Determinate

Intentions:

Gives users an idea that a button has been pushed and request has been executed with an idea of the loading progress
Gives users an idea that e.g. a page is loading with an idea of the loading progress

Content loading

MediaViewer - loading image

Tool loading

Visual Editors - loading tool (OOUI ProgressBarWidget), utilizes "Ori Livneh mind control" technique