What a Referral Link Is
A referral link turns a happy user into an acquisition channel. The app gives each user a unique link, the user shares it with friends over WhatsApp, Instagram, SMS or email, and every install that comes through the link is credited to them. Most programs reward both sides: the referrer gets credit or cash, the invitee gets a discount or bonus.
The link carries the referrer's identity, usually as a code or ID in a query parameter. That one value is what connects a new user to the person who invited them, so the whole program depends on it surviving every step from tap to sign-up.
How Referral Links Work for Apps
On the web, a referral link is simple: the code is in the URL, and the site reads it. Apps add a hard step in the middle, the app store, which does not pass URL parameters through to the app.
Deferred deep linking solves this. When the invitee taps the link, the link service records the click and the referrer code. If the app is installed, it opens to the referral screen with the code. If not, the invitee goes to the store, installs, and on first open the app asks the MMP for the deferred deep link. The code comes back with it, and the app can show a personalised welcome such as "Asha invited you, here is your bonus" and apply the reward once the invitee qualifies.
Without this, the invitee lands on a generic onboarding screen, the referral is lost, and support tickets start arriving from referrers asking where their reward is.
Designing a Referral Program That Works
Make sharing easy. Put the invite screen where satisfied users already are, such as after a successful order or a milestone, and offer the share targets your users actually use. In India, that usually means WhatsApp first.
Make the reward clear and fair to both sides. Rewards that only benefit the referrer feel like spam to the invitee. Make the qualifying action meaningful, such as a first purchase rather than an install, so you pay for real users.
Make the invitee's first screen match the promise. If the message said "get 100 rupees off your first order," the first thing the invitee sees should confirm that offer.
Measuring Referrals
Measure the full funnel: invites sent, clicks, installs, sign-ups and qualifying actions, per referrer and in total. Then compare referred users with other channels on retention, revenue and cost. Referred users often retain better because a friend vouched for the app, and that is the case for funding the reward.
The viral coefficient, or k-factor, combines invites per user and invite conversion into one number that shows how much growth each user generates. Track it over time and by cohort.
Referral Links in Linkrunner
In Linkrunner, any link on your subdomain that carries a referral code in the referrer parameter is reported under the Referrals channel, with clicks, installs, sign-ups and revenue. You do not need to create a campaign for each referrer. The app reads the code from the deferred deep link on first open. Linkrunner also accepts AppsFlyer's af_referrer_customer_id and af_referrer_uid parameters, which helps when migrating an existing program. To report a referral program as its own campaign instead, add the parameter to a campaign link. See referral links for setup.
Preventing Referral Abuse
Rewards attract abuse. Watch for many referrals from the same device, IP address or payment method, referrers whose invitees never return after the reward, and self-referrals through second accounts. Reward on actions that are expensive to fake, cap rewards per referrer, and hold payouts until a short review window passes. A small amount of friction for bad actors protects the program for everyone else.
Referral Links and Attribution Priority
Referral links compete with other channels for credit. A user might see an ad, then receive a friend's invite, then install. Which one gets the install depends on your attribution rules, usually the last click within the lookback window.
Decide how you want referrals treated before launch. If the referral reward is paid by your app, you probably want the referral to be recorded even when a paid click also claims the install, so the referrer is rewarded fairly. In that case, store the referral code in your own backend from the deferred deep link, independent of which channel the MMP credits.
For reporting, keep two views: channel attribution, which shows where installs came from for budget decisions, and referral credit, which shows who earned rewards. They answer different questions and will not always match. Explaining that difference early saves arguments in growth reviews later.