We accept 2x density image files for use on desktop and mobile devices that have high-density, or "Retina," displays, such as mobile phones and 4K monitors. This can help address pixelation or blurriness concerns when standard resolution creative is used on site.

These can be supplied for all standard IAB sizes unless being used within impression based roadblock executions. 

Density refers to the number of pixels packed into a specific area, while size, or creative dimensions, refers to the physical space available for display on the screen. A double-density screen contains twice as many pixels within the same area.

Standard density is a 728x90 image displayed dimensionally as 728x90 on the screen.

Double density is a 1456x180 image displayed dimensionally as 728x90 on the page.

How to Include Double Density in HTML5 Zip Creative

HTML5 creatives can also be designed for double density. In a double-density HTML5 creative, all images are twice the size in terms of dimensions but are scaled down to their correct display size using HTML markup or CSS.

In the following example code snippet from a 300x600 creative, every image is dimensionally twice as large as its physical size on the screen:

<img class="ad-background" src="http://ad-server.com/image/background-600x1200.jpg" width="300" height="600" />

<img class="ad-button" src="http://ad-server.com/image/button-100x100.png" width="50" height="50" />

<img class="ad-image" src="http://ad-server.com/image/dog-300x250.gif" width="150" height="125" />

Regardless of whether you define the dimensions in HTML or CSS, they should always match the actual display dimensions on the screen. Only the images themselves should be double the size. It's a good practice to check your creative in the browser to ensure all images are displayed at the correct size