추천과 바이럴 순환 구조 구축

Paid acquisition stops the moment you stop paying. A viral loop turns users into recruiters, creating growth that compounds for free.

This lesson explains referral mechanics and how to measure their power.

A viral loop is a cycle where existing users invite new users, who in turn invite more. Each turn of the loop amplifies reach without new ad spend.

The classic example: a user shares an invite, a friend joins, and the friend shares again.

The K-factor measures virality: how many new users each existing user brings.

Suppose each user sends 5 invites and 20% convert:

Strong referral programs offer a double-sided incentive—both the referrer and the new user benefit. This boosts both invite rate and conversion.

Match the reward to your economics so it stays profitable.

Every extra tap kills referrals. Make sharing one step: prefilled messages, deep links, and native share sheets.

The lower the friction, the higher the invites-per-user, which directly raises K.

Deep links carry the referrer code so new installs are attributed correctly and rewards are credited automatically.

Virality depends not just on K but on cycle time—how fast a loop completes. A K of 1.2 that loops weekly grows far faster than one that loops yearly.

Shorten the time from invite to activation.

Referral rewards attract fraud: fake accounts, self-referrals, bots. Protect your program with device checks, activation requirements before payout, and rate limits.

Not all virality is a referral program. Inherent virality happens when using the app naturally exposes others to it (shared documents, multiplayer, content shared publicly).

Build sharing into the core experience where possible.

Even a sub-1 K-factor is valuable: it amplifies every paid install. If paid brings 100 users and K is 0.5, you effectively get 200 over the loop life—halving your real CAC.

Test your understanding of viral loops.

You learned to build compounding growth:

• A viral loop turns users into recruiters.
• The K-factor = invites × conversion measures virality.
• Use double-sided incentives, low friction, and deep links.
• Even K < 1 lowers your effective CAC alongside paid channels.