Manual:$wgLogoHD

Server URLs and file paths: $wgLogoHD
URLs for HD versions of the site logo.
Introduced in version:1.25.0 (Gerrit change 195195; git #b5f2cf2d)
Deprecated in version:1.35.0 (Gerrit change 562588; git #8cd2e133)
Removed in version:1.42.0 (Gerrit change 992794; git #167fbd0a)
Allowed values:(array of factors and relative paths or urls)
Default value:false

Details edit

Array with factors and their associated relative paths or URL paths to HD versions of the wiki logo. The scaled logo size should be under 135x135 pixels, the same as the size should be for the file of $wgLogo .

Only 1.5x and 2x versions are supported. That means e.g. the 2x version should be a square and should maximally have 270x270 pixels.

Example:

$wgLogoHD = [
	"1.5x" => "path/to/1.5x_version.png",
	"2x" => "path/to/2x_version.png"
];

Older MediaWiki versions edit

If you're using MediaWiki versions older than 1.25, you can add the following snippet to your MediaWiki:Common.css:

@media (-webkit-min-device-pixel-ratio: 1.5), (min--moz-device-pixel-ratio: 1.5), (min-resolution: 1.5dppx), (min-resolution: 144dpi) {
	#p-logo a {
		background-image: url(//path/to/1.5x_version.png);
	}
}
@media (-webkit-min-device-pixel-ratio: 2), (min--moz-device-pixel-ratio: 2), (min-resolution: 2dppx), (min-resolution: 192dpi) {
	#p-logo a {
		background-image: url(//path/to/2x_version.png);
	}
}

See also edit