IAB banner specs
The following IAB banner specifications are for Workbench and Google Ad Manager.
Animated banners (animated GIFs) can loop only three times, and the total animation can’t exceed 15 seconds. Repetitive or rapid flashing, blinking in excess, or visually stressful animations aren’t allowed.
Assets may only be produced as JPEG, GIF, or PNG. Specifications are optimized for all supported devices.