Viral loops

A viral loop: one user triggers more users to join. K-factor (invites × conversion rate) determines if it grows. K > 1 = true viral.

Types

• Incentive-based (refer-a-friend rewards)
• Utility-based (Dropbox, need to share files)
• Social (WhatsApp, need the other person to receive)
• Content-based (Reddit posts drive more users)

Rarely K > 1

Most products claiming virality have sub-1 K-factors. They still benefit (lower CAC) but don't grow on their own.

Building

• Make sharing the natural path
• Reward both sides (sender + receiver)
• Shorten the cycle (time from invite to active)
• Track K-factor explicitly

Common failure

Adding a referral program to a product nobody shares organically. Fix the product first.

What to do with this

• Measure actual K-factor instrument-based, not self-reported, most "viral" products have K under 0.3 on close measurement
• Make sharing the natural path of value delivery, not a bolted-on referral program, products that require sharing to work have real K
• Reward both sides (sender + receiver) when incentivizing, one-sided referrals produce lower uptake than two-sided
• Shorten the loop cycle time, cutting invite-to-active from 14 days to 3 days is often higher ROI than raising K
• Don't count on K over 1 to scale the business, even strong viral products stack paid + content on top of virality for most of their growth