BuildBrief: How Viral Loops Scale Your App for Free

Most apps grow linearly. You get 10 users, then 20, then 30.

But the best apps grow exponentially. 10 users become 100. 100 become 1,000. 1,000 become 10,000.

The difference? They have implemented something called a viral loop.

And once it kicks in, the snowball effect takes over.

What is a viral loop?

A viral loop is simple:

Someone uses your app → They share it → Their friends join → Those friends share it too

That's it. That's the infinite engine.

It's an engineered system where existing users naturally invite new users, who then repeat the cycle.

3 types of Viral loops:

1. Incentivized (both users get rewarded): Dropbox invites a friend, both get 500 MB free storage. The reward is the product itself, making it feel like a gift, not spam.

2. Social/UGC (users share to show off): Spotify Wrapped shows your top 5 artists and listening stats. So shareable that millions post to their stories, driving friends to download Spotify.

3. Collaborative (requires others to work): Figma requires you to invite teammates to collaborate on designs. The product is useless alone, so virality is built into its core utility.

The key: sharing isn't a favor - it's either rewarded, celebrated, or required to use the product.

The viral loop starts slow, but the more users you get - the faster it grows (exponentially). You're not adding users, you're multiplying them.

And this significantly decreases your spend per new customer.

Let's say you pay $200 to get 1,000 new users.

But each of these users invites an average of 2 new friends.

You've spent $200 not for 1,000 users, but for 3,000 new users.

How to build your viral loop

Building a viral loop isn't about adding a "share" button. It's about making sharing core to the experience.

Step 1: Identify what users want to share

People share things that make them look good, feel good, or help them win.

What achievement in my app would users want to show off?

What result would make them say "look what I did"?

What problem does my app solve that their friends also have?

Step 2: Make sharing give them something back

Sharing should feel like progress, not a favor.

Examples:

Unlock a premium feature when 3 friends join.

Get bonus points, credits, or lives when someone uses your referral.

Make the app more fun or useful with friends (multiplayer, leaderboards, challenges).

Step 3: Make it ridiculously easy

The harder it is to share, the fewer people will do it.

Do this:

Generate a unique referral link automatically.

Pre-fill the share message with something compelling.

Let them share to multiple platforms with one tap.

Show them exactly what they'll get when someone joins.

Step 4: Close the loop

When a new user arrives, make sure they understand the value immediately and can start their own sharing cycle.

The flow:

New user clicks referral link → Sees what they get → Signs up in seconds → Experiences the "AHA moment" → Gets their own referral link → Shares it.

If any step is broken, the loop dies.

Action steps:

1. Map out your current user journey and identify where sharing would feel natural
2. Design a reward that makes sharing feel like progress, not a favor
3. Build the simplest version: referral link + reward + easy sharing
4. Then watch your app grow on its own.

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Happy building!
– Kristoffer, BuildWithAI