Viewport

Viewport in web browsers is the visible visible area of a entire web page. If the document is larger than the viewport, the user can shift the viewport around by scrolling.

wikipedia:HTML5 in 2014 introduced a method to let web designers take control over the viewport, through the tag:

<meta name="viewport">

.

It improves visualization in different screen sizes helping visualization in phones or tablets.

In Mediawiki software can be configured by adding to LocalSettings.php:

$out->addHeadItem('viewport', '<meta name="viewport" content="width=device-width">');