When should an advertiser, who's using Campaign Manager 360 to run an in-stream video ad campaign, consider activating default ads for placement?

In Campaign Manager 360, an advertiser should consider activating default ads when serving ads to any user or device because the default ad acts as a critical safety net to ensure that an impression is never wasted. Regardless of whether the target is a desktop, mobile, or tablet user, if a specific campaign-assigned ad cannot serve due to technical issues, strict targeting restrictions, or flight date expirations, the system will fallback to the default ad to fill the placement. This is particularly vital for in-stream video, where publishers require a creative to be delivered once the ad request is made; by having a default ad ready for any device type, you maintain a 100% fill rate and protect the integrity of the user experience by avoiding broken players or empty ad slots.