Understanding the Large Rectangle Format
The 336x280 large rectangle is an expanded version of the ubiquitous 300x250 medium rectangle. While it was not part of the original IAB Universal Ad Package, Google adopted it as one of its top-performing ad sizes on the Google Display Network. The additional 36 pixels of width and 30 pixels of height give advertisers roughly 12% more creative real estate, which can translate into higher click-through rates due to more impactful visuals and larger call-to-action elements. The format is particularly effective for product-focused ads where the extra space allows for clearer product imagery.
Where to Place the 336x280 on Your Page
The large rectangle works best in the same positions as the 300x250: embedded within article content or placed in a sidebar. Because of its slightly wider footprint, ensure your content area or sidebar can accommodate 336 pixels of width plus any padding. For standard blog layouts with a content column of 700px or wider, an in-content 336x280 unit fits comfortably with text wrapping around it. In sidebars, verify that the sidebar width is at least 360px to provide adequate breathing room. If your layout cannot guarantee the space, implement responsive ad tags that fall back to 300x250 when the container is too narrow.
Revenue Comparison with 300x250
Publishers who can accommodate the 336x280 alongside the 300x250 in their ad setup often see a measurable revenue lift. Google has reported that the large rectangle is among the top-performing sizes by eCPM, partly because it offers advertisers more creative flexibility and partly because it has lower supply compared to the saturated 300x250 market. When configuring Google AdSense or Ad Manager, set your ad slot to accept both sizes to maximize competition in the auction. The ad server will automatically select the highest-paying creative that fits the available space.
Creative Guidelines and Best Practices
Design for the 336x280 follows the same principles as the medium rectangle, with the advantage of extra space. Use the additional area to increase font sizes for better readability, add a secondary line of copy, or enlarge your product image. Keep file sizes under 150KB for static images. Include a clearly defined border or background color to distinguish the ad from surrounding page content, as required by most ad network policies. When creating responsive ad sets, always design both the 336x280 and 300x250 versions simultaneously to maintain visual consistency across placements.