A broken ad call, also known as an ad call failure, is a situation in which an ad server is unable to serve an ad to a website or app. This can happen for a variety of reasons, such as a network or server error, an issue with the ad creative, or a problem with the ad tag on the website or app. When a broken ad call occurs, the website or app will typically display a placeholder, a backup ad, or error message in place of the ad. This can be frustrating for users and can also have negative consequences for the advertiser, such as lower ad performance and revenue. Advertisers can use a variety of techniques to minimize the occurrence of broken ad calls, such as testing and optimizing their ad creative and ad tags, and monitoring their ad server performance.