What matters
Google Display Ad — 336×280 Large Rectangle dimensions at a glance
The 336×280 Large Rectangle offers slightly more canvas than the popular 300×250. It's commonly placed within content areas for inline advertising.
The extra space compared to 300×250 allows for slightly more impactful creative while maintaining broad placement availability.
Using the same creative as 300×250 without adjusting leaves unused space. The extra pixels should add value, not just padding.