The viral coefficient (k-factor) measures built-in user-to-user growth: the number of new users each existing user generates, computed as invitations sent per user multiplied by the conversion rate of those invitations. At k = 0.5, every 100 users recruit 50 more (who recruit 25, and so on — amplifying but converging); at k > 1, each generation is larger than the last and growth is self-sustaining without paid acquisition. Sustained k above 1 is extraordinarily rare and almost always temporary; real products use virality as a multiplier on other channels, and viral cycle time — how fast a loop completes — often matters more than the coefficient itself.
Mechanically, virality is engineered through loops: inherent collaboration (documents shared to be edited), artefact exposure (“made with” footers, public links), incentivised referrals (give-get offers), and network invitations. Each loop is instrumented and optimised like any funnel — invitations per user, acceptance rate, activation of the invited.
Legal limits of growth loops
Invitation mechanics process third-party personal data: the friend’s email or phone number is personal data of someone who never consented, which is why contact-book uploads and auto-invites have drawn data-protection enforcement globally and sit uneasily under KVKK’s lawful-basis architecture. Unsolicited invitation messages can qualify as commercial electronic communications requiring consent under Türkiye’s e-commerce law and İYS regime. Referral rewards must avoid misleading-advertising territory and, in regulated verticals (finance, health, gambling-adjacent mechanics), sector rules on inducements. The durable pattern: user-initiated, transparent sharing with the inviter as the visible sender — engineering the loop around consent rather than around its absence.
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