Referral Program in Mobile App

Implementing a Referral Program in Mobile Apps

A referral program is attribution on the mobile platform, not just "share a link". The main technical challenge: linking app installation to a specific referrer when days can pass between clicking the link and opening the app, and devices can change.

Deep linking and deferred deep linking

Regular deep link doesn't work: if the app is not installed, the user lands in App Store and the link is lost. You need a deferred deep link — a mechanism where the link is "remembered" and passed to the app on first launch after installation.

Tools: Branch.io, Firebase Dynamic Links (deprecated from 2025, not recommended for new projects), AppsFlyer OneLink, Adjust. Branch is most universal.

// iOS — Branch SDK
Branch.getInstance().initSession(launchOptions: launchOptions) { params, error in
    if let referrerID = params?["referrer_id"] as? String {
        // First launch with referral parameter
        ServerAPI.attributeInstall(referrerID: referrerID, newUserID: currentUser.id)
    }
}

Branch tracks link clicks via fingerprinting (IP + User-Agent + time) and matches with installation in a 2-hour window. Accuracy ~85-95% — not 100%, but sufficient for business metrics.

Generating referral links

Each user gets a unique short link:

let linkProperties = BranchLinkProperties()
linkProperties.channel = "app_share"
linkProperties.feature = "referral"

let universalObject = BranchUniversalObject(canonicalIdentifier: "referral/\(userID)")
universalObject.contentMetadata.customMetadata["referrer_id"] = userID

universalObject.getShortUrl(with: linkProperties) { url, error in
    self.referralLink = url
}

On Android — similarly through Branch SDK for Android.

Attribution and bonus crediting

After successful attribution (new user installed and opened app) — server logic:

1. Check that new_user_id is truly new (no previous sessions, no device fingerprint match with existing accounts — to protect against fraud via reinstalls)
2. Create record in referral_attributions: referrer_id, referred_id, attributed_at, status=pending
3. Credit bonus to referrer only after condition is met — for example, after first purchase of referral or after 7 days of activity

Cannot credit early: user installs, gets bonus for referrer, uninstalls — this is garbage traffic.

Conditions and anti-fraud

Basic protections: one referral bonus per device (device_id), limit on referrals per month, minimum account age for referrer to participate (e.g., 7 days).

For serious volumes — integrate with anti-fraud service (Adjust Fraud Prevention, Branch Fraud Protection): they check behavioral patterns and emulator signals.

Screens in app

Referral program page: current referral bonus balance, number of invited, history of credits, "Share" button with native share sheet.

Estimated time — 3–5 days: Branch SDK integration (iOS + Android), server attribution logic, basic anti-fraud, UI screens.