User acquisition (UA) is the process — and the associated spending — of attracting new users to a product, app, website, platform, or service through marketing and advertising. It encompasses the total investment made to bring in new customers or users, and it's a core discipline for any business that grows by expanding its user base, especially mobile apps, SaaS products, games, and digital platforms. In essence, user acquisition is the engine of growth: the systematic effort to turn marketing spend into new users.
 

UA is measured by efficiency metrics that connect spend to results. Cost per acquisition (CPA) measures the cost of acquiring a user who completes a defined action. In mobile apps specifically, cost per install (CPI) measures the cost of each new app install. Customer acquisition cost (CAC) captures the total cost of acquiring a paying customer. These metrics tell UA managers exactly what growth is costing and whether it's sustainable.
 

The critical principle of user acquisition is that the cost of acquiring a user must be justified by the value that user generates. This is the relationship between CAC and lifetime value (LTV) — the total revenue or profit a user delivers over their entire relationship with the product. If it costs $20 to acquire a user who generates $100 in lifetime value, UA is profitable and scalable. If acquisition costs exceed lifetime value, growth is destroying money. Sophisticated UA is therefore obsessed not just with acquiring users cheaply, but with acquiring valuable, high-retention users — because a cheap user who churns immediately is worse than an expensive user who stays and spends.
 

User acquisition campaigns run across many channels: programmatic advertising through DSPs, paid social, search, app store optimization, influencer marketing, and more. In mobile, UA relies heavily on in-app advertising, with formats like interstitials, rewarded video, and playable ads driving installs, and on precise targeting to find users likely to engage and convert. Programmatic enables UA at scale, reaching potential users across the open web and app ecosystem with data-driven targeting and real-time optimization toward acquisition goals.
 

UA is a data-intensive, continuously optimized discipline. Managers test channels, audiences, creatives, and offers, measuring which combinations acquire the most valuable users at the lowest cost. They optimize toward downstream value — not just installs or sign-ups, but engaged, retained, revenue-generating users — using post-acquisition metrics like retention, activation, and LTV to guide spend allocation.
 

Fraud is a serious threat to UA, particularly in mobile. Install fraud, fake users, and bot traffic can consume budgets and corrupt data, making fraud detection and mobile measurement partners essential to ensure acquired users are real and valuable.
 

For growth-driven businesses, user acquisition is mission-critical — the function that converts marketing investment into the expanding, valuable user base that fuels the entire enterprise. Done well, it's a disciplined, measurable growth engine; done poorly, it's an expensive way to attract users who never deliver value.