“When you run web campaigns and app install campaigns on Meta at the same time, you're not reaching the same pool of users twice. Meta's algorithm finds different user profiles for web objectives versus app install objectives. It's genuinely additive inventory.”

Running web and app install campaigns on Meta simultaneously reaches different people, not just more of the same

Petit's most counter-intuitive finding: web and app campaigns on Meta do not cannibalise each other. Meta optimises each campaign type differently — web conversion campaigns find users who respond to landing page CTAs, while app install campaigns find users comfortable tapping directly to the store. Running both simultaneously expands total reachable audience rather than just splitting budget against the same people. This is why ROAS on web often holds even after scaling app campaigns.