Do You Have a Viral Loop?

From the Jason Calacanis startup checklist.

A viral loop means one user is incentivised to create more users. The best viral loops apply the Hook Model's trigger, action, and variable reward to user acquisition itself.

Robinhood's Referral Programme

Robinhood's free stock referral is one of the most effective viral loops ever built:

• Invite a friend → both of you get a free stock
• The trigger and action are clear and frictionless
• The reward is variable — you don't know what stock you'll receive; it could be Apple or a penny stock

Why it worked so well: over 50% of Robinhood's users were first-time investors. The hardest step for a first-timer is linking a bank account, depositing funds, and making that first trade. By giving them a free stock, Robinhood put skin in the game instantly — removing every barrier at once.

Result: per their S-1, over 80% of users were acquired organically or through referrals.

Other Examples

Dropbox — free storage referrals. Dropbox Basic users earned 500MB of extra storage for every friend they referred, up to 16GB. Storage was the core value of the product, so giving away more of it was the obvious reward.

Words With Friends — frictionless friend invites. A user challenges a friend to play Scrabble. If the friend doesn't have the app, WWF sends them a download link. Once they're in, they can invite their own friends — and the loop continues.

The question to ask

Can you leverage your core product to create a referral incentive that is as natural, frictionless, and rewarding as Robinhood's free stock? The best viral loops use the product itself as the reward.