Introduction to install bids#

CPI versus tCPI bidding for install campaigns#

While the goal of install campaigns is always to net the most app installs possible, Android and iOS install campaigns use different bidding models because they follow different billing models.

Android CPI bids#

Android campaigns use cost per install, or CPI billing. CPI is a pricing model that bills advertisers the specified bid price each time an install is attributed to their campaign. As such, the advertiser pays the exact bid price when an attributed install occurs.

iOS tCPI bids#

iOS campaigns use cost per impression, or CPM billing. CPM is a pricing model that bills advertisers based on the number of impressions their campaign receives. As such, iOS campaigns use target cost per install, or tCPI bidding. The advertiser sets the desired amount to pay per install, which Unity optimizes towards based on eCPMs and creative performance.

Unity’s tCPI model differs slightly from traditional industry CPM models. In a traditional industry CPM campaign, you pay a predefined amount per thousand impressions (cost per mille, or CPM) that your ad receives. In this model, you serve ads to anyone matching your campaign’s targeting criteria, and you pay the same amount for each impression.

Unity serves ads to users who are most likely to install your app. You pay a dynamic price depending on the potential value of the player. The price is tied to the probability that the impression will convert to an install. Using this model, Unity targets impressions that are likely to translate to your target CPI.