Viral Loops and Referral Programs

The viral coefficient (K) measures how many new users each existing user brings in. If K is above 1.0, the product grows exponentially without additional marketing spend. K is calculated as: K = invitations sent per user × conversion rate of invitations. A K of 0.5 means two users bring in one additional user — still meaningful but not fully viral.

Viral loops are the specific product flows that enable sharing: invite a friend by email, share a creation to social media, embed a widget on an external site. Each loop must be designed so the sharing action provides clear value to both the sharer and the recipient, otherwise adoption stalls at the point of invitation.