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Cost Per Mille (CPM), also known as cost per thousand impressions, is an advertising pricing model where advertisers pay a fixed rate for every 1,000 times their ad is displayed to users. "Mille" is Latin for thousand. CPM is one of the most common buying models in digital advertising, particularly for brand awareness campaigns and display advertising. In the mobile app ecosystem, CPM is used both by app developers buying ads to acquire users and by app publishers selling ad inventory within their apps. For user acquisition, CPM campaigns are typically less performance-oriented than CPI or CPA models, since the advertiser pays for visibility rather than a specific action. However, CPM can be effective for reaching large audiences at scale and building brand recognition. For app publishers monetizing with ads, CPM represents the revenue earned per 1,000 ad impressions served — also called eCPM (effective CPM) — and is a core metric for evaluating ad monetization performance across different ad networks and formats.

CPI stands for Cost Per Install, meaning the cost that an advertiser pays each time a user installs their mobile app after clicking on an ad. CPI is a performance-based pricing model, which means that the advertiser only pays for results that directly contribute to their business goals, such as app installations. This pricing model is particularly popular among mobile app developers who want to promote their apps and acquire new users.

Creative fatigue occurs when an advertising audience has been exposed to the same ad creative too many times, resulting in declining click-through rates, rising cost per install, and diminishing campaign performance. In mobile user acquisition, creative fatigue is one of the most common reasons for campaign degradation over time. As users see the same images, videos, or messaging repeatedly, they begin to ignore the ads — a phenomenon sometimes called "ad blindness." Detecting creative fatigue early is critical for maintaining efficient UA spend. Key indicators include a decline in CTR while impressions remain stable, rising CPIs, and lower conversion rates from impression to install. Growth teams combat creative fatigue by maintaining a pipeline of fresh creatives, systematically rotating ad variations, testing new concepts and formats, and segmenting audiences to control frequency exposure. Apps running web funnel campaigns face similar dynamics — landing page designs and value propositions must be periodically refreshed to sustain conversion rates.

Impression-to-install rate (also called IPM — Installs Per Mille, or installs per thousand impressions) measures the percentage of ad impressions that ultimately result in an app install. It is calculated by dividing the number of installs by the number of ad impressions and multiplying by 100 (or by 1,000 for the IPM variant). This metric combines ad engagement efficiency (do people click?) with post-click conversion efficiency (do people install after clicking?), making it a holistic measure of creative and targeting quality. A high impression-to-install rate indicates that the ad creative resonates with the target audience and that the app store listing or landing page effectively converts interested users. Typical impression-to-install rates vary significantly by ad format and vertical, with video ads and rewarded formats generally outperforming static banners. Monitoring this rate across different creatives, audiences, and placements helps growth teams identify their most efficient combinations and detect creative fatigue early.

User acquisition refers to the strategies and activities used to attract new users to a mobile app or platform. It encompasses paid advertising, organic discovery, and referral programs working together to drive installs and grow an engaged user base.