App Cross-Promotion Explained: The Cheapest Install Source You Already Own

If you run more than one app, you have probably heard someone say cross-promotion is basically free. I have leaned on it for years, and I would not call it free, but it is usually the cheapest install source I have. You are moving people you already reach from one product to another, so you skip the auction and the media cost that comes with buying strangers.

The catch is that cheap does not mean automatic. Done well, cross-promotion fills a new app with warm users at almost no marginal cost. Done carelessly, it quietly damages the app you promote from and brings over people who never open the second app again. Here is how it works, when it makes sense, and how I measure whether it is really adding installs or just moving them around.

What app cross-promotion actually means

Cross-promotion is the practice of pointing users of one app toward another. The simplest version is a company with a portfolio: a photo editor promoting a video editor, a budgeting app promoting a bill-tracking app, a puzzle game promoting the studio's next title. You control both sides, so you can put a house ad, a banner, or a full-screen interstitial inside the first app that sends people to install the second.There are a few common shapes this takes, and it helps to know which one you are looking at:

• Owned cross-promo networks: a company runs its own placements across all of its apps, deciding centrally which app to promote where. Big game studios do this at scale.
• In-app placements: the actual real estate, such as banners, interstitials between levels, a card in a feed, or a nudge on a settings screen.
• Cross-promo ad networks: third-party networks that let smaller publishers pool inventory and trade installs with each other on a house-ad basis.
• Publisher swaps: two companies agree to promote each other directly, often measured so the trade stays roughly even.

The thread running through all of these is that you are not bidding against other advertisers for a cold audience. You are using attention you already earned, which is why the economics look so different from a normal paid channel.

Why it is often the cheapest install source

When you buy installs on Apple Search Ads or Meta, you pay for every impression or click regardless of whether it converts, and you are competing with everyone else who wants that same user. With cross-promotion, the impression is inventory you own. You are not paying a network to show it, so the marginal cost of one more impression is close to zero.That changes the math. A paid channel might cost you a few dollars per install once you account for the auction and the conversion rate. An owned cross-promo placement can deliver installs for cents, because the only real cost is the attention you spend inside the host app. For a company sitting on a portfolio with steady traffic, that inventory adds up to a meaningful number of installs every month without touching the media budget.There is a second reason it converts well. Someone using your photo app already trusts your brand and cares about the problem space, so a relevant second app is an easier sell than a cold ad to a stranger. Warmer audience plus near-zero cost is a hard combination to beat, which is why I check cross-promotion before spending on anything paid.

A simple way to plan and size it

You do not need a model to decide whether cross-promotion is worth setting up. Decompose a plan into three numbers and you get a usable estimate in a few minutes.The chain is impressions x click-through rate x install rate. Impressions is how many times you can show the placement, roughly your host app's active users times how often each one sees it. Click-through rate is the share who tap it, and install rate is the share of those who finish the store install.Say your host app shows the placement to 500,000 users a month, click-through is 3 percent, and install rate is 40 percent. That is 500,000 x 0.03 x 0.40, or 6,000 installs a month at basically no media cost. Now compare that to what 6,000 paid installs would cost you and the value is obvious.The same decomposition tells you where to push. If click-through is weak, the creative or placement is the problem. If install rate is weak, the store listing or the promise-to-payoff match is off.

How to measure it without fooling yourself

The number that matters is incremental installs, meaning installs that happened because of the cross-promotion and would not have happened otherwise. This is where teams trick themselves. Some people who install your second app through a house ad were going to find it anyway through search or word of mouth, so counting every attributed install as a win overstates the impact.The bigger trap is cannibalization. If both apps compete for the same moment or the same spend from the same person, moving a user from app A to app B might not grow the business at all. You just shifted revenue from one line to another and paid for it with app A's attention. Complementary apps rarely have this problem, and substitute apps almost always do.To measure it honestly, run a holdout. Show the placement to most of your host-app users and withhold it from a random slice, then compare install and revenue outcomes across both apps between the two groups. Lean on your mobile measurement partner for clean attribution, and always read the portfolio total, not just the app you are promoting. If the second app grows while the first one quietly shrinks, that is not a win, and only a combined view will show it.

When it makes sense and where it goes wrong

Cross-promotion works best when the audiences are complementary rather than identical. A person who tracks their spending is a natural candidate for a bill reminder app. A casual puzzle player is a reasonable target for another casual title from the same studio. The closer the overlap in need without full substitution, the better the trade.The first pitfall is promoting to the wrong segment. Blasting every user with the same house ad ignores that some of them are your best-paying customers in the host app, and distracting them is the last thing you want. Segment first, promote the second app to the users most likely to want it, and hold back the ones deeply engaged where they are.The second pitfall is hurting the host app's retention. Every interstitial you show for another app is attention taken away from the experience someone came for. Push too hard and you nudge users toward the exit, which means you traded a few cheap installs for a real drop in the app that was funding everything. I keep placements relevant and capped, watch host-app retention closely while a campaign runs, and pull back the moment core metrics dip. Cheap installs are only cheap if the source stays healthy.