320x50

320x50 refers to a digital display advertising banner that is 320 pixels wide and 50 pixels tall. It is commonly known as a mobile leaderboard and is one of the standard ad unit sizes defined by the Interactive Advertising Bureau (IAB). The format is designed for compact placements on mobile websites and in mobile apps, where horizontal space is at a premium.

The size emerged with the early expansion of mobile advertising and became a widely supported unit across publishers, ad networks, and exchanges. Its small footprint allows it to load quickly and fit unobtrusively into various page layouts, contributing to broad compatibility with both desktop and in-app environments. As mobile advertising evolved, 320x50 remained a staple alongside other IAB sizes such as 300x250 and 728x90.

Technical aspects include support for multiple creative formats, including static images, animated GIFs, and HTML5 rich media. Creatives are delivered by ad servers and programmatic platforms, and the unit is often constrained by platform-specific requirements such as file size, animation limits, and interaction rules. In practice, 320x50 banners appear as part of a larger inventory strategy and may be complemented by related sizes like 320x100 for extended branding.

In performance terms, effectiveness is typically measured by impressions, click-through rate, and post-click engagement, with ad quality and page context influencing visibility. While still common, publishers increasingly pair 320x50 with responsive or dynamic designs to fit varying screen sizes and layouts. Related sizes include 320x100 and other IAB banner units.