Advertising inventory or media inventory is the space available in the media, advertising, and marketing industries to advertisers on newspapers, magazines, and digital platforms.
[1] Traditionally advertising inventory was sold during upfront events in the third week of May.
[2][3] However, advertising space is increasingly being transacted algorithmically, such as with real-time bidding.
[4] Media space is typically broken down into four categories, which can be purchased through a variety of sales channels.
[5]