A daisy chain is a series of transactions in which an advertiser buys media inventory from one publisher, who then turns around and buys more inventory from another publisher, and so on. Often there are also ad networks acting as intermediates. This can create a chain of transactions in which each publisher is buying inventory from the next, and the original advertiser is buying from the last publisher in the chain.

Daisy chaining is commonly used in the display advertising industry as a way for advertisers to access a larger pool of inventory and reach a wider audience. By buying inventory from multiple publishers, advertisers can reach more users and increase the visibility of their ads.

However, daisy chaining can also create challenges for advertisers and publishers. For advertisers, it can be difficult to track and measure the effectiveness of their ad campaigns when the inventory is bought through multiple publishers. For publishers, it can be challenging to ensure that the inventory they are buying is of high quality and will generate revenue.

To manage these challenges, businesses often use attribution models and cross-device tracking and conversion tools to get a complete picture of the customer journey.