Growth Loops
Reforge's framework that replaced funnels with self-sustaining loops—where outputs become inputs.
Funnels were the dominant growth model for a decade—pour users in at the top, optimize conversion, measure AARRR. But funnels don't explain how the fastest-growing products actually grow. Growth loops do. The output of one cycle becomes the input for the next. Users don't just convert—they create more users. That's compounding growth.
The output becomes the input. That's the loop. That's compounding.
Viral Loops
Users invite other users because the product is better with more people in it. Network effects drive acquisition directly through the product experience.
Example: Dropbox's referral program gave both parties more storage. Users shared files → recipients needed Dropbox → new users invited more users.
Content Loops
Users create content that attracts new users via search and discovery. User-generated content becomes the acquisition channel.
Example: Pinterest users pin content → content ranks in Google → searchers discover Pinterest → new users create more content.
Paid Loops
Users generate revenue that funds acquisition of more users. Monetization feeds growth directly—if LTV > CAC with margin for reinvestment.
Example: SaaS companies convert users → revenue generated → funds paid ads → acquires more users → more revenue.
Sales Loops
Usage creates more sales opportunities within or across organizations. Product usage generates pipeline and expansion revenue.
Example: Slack users add coworkers → teams expand → department adopts → company-wide rollout → new companies discover via word of mouth.
User-Generated Content (UGC) Loops
Users create public-facing content that's distributed outside the platform, bringing new users back in.
Example: YouTube creators publish videos → shared on social → viewers click through → new viewers become creators → more videos.
Product-Led Growth (PLG) Loops
Free users create value that attracts paid users. Freemium drives adoption; premium drives monetization and expansion.
Example: Figma designers share files → stakeholders view → teams adopt → upgrade to paid → more users join teams.
The insight: funnels are linear, loops compound. Funnels require constant input—stop pouring, stop growing. Loops feed themselves. One user creates multiple users. That's exponential, not linear. That's why companies obsess over loops.
Brian Balfour (founder/CEO of Reforge, former VP Growth at HubSpot) and Casey Winters (CPO at Eventbrite, formerly Pinterest and Grubhub) developed the growth loops framework in the mid-2010s through their work with high-growth startups and later codified it at Reforge.
Reforge launched in 2017 as a professional development platform for growth practitioners. The growth loops framework became central to Reforge's curriculum—particularly in the Growth Series and Advanced Growth Strategy programs co-created with Kevin Kwok (formerly Greylock Partners) and Andrew Chen (GP at a16z, former growth at Uber).
In 2019, Balfour, Winters, Kwok, and Chen published "Growth Loops are the New Funnels" as part of a four-part essay series. The article articulated why the AARRR funnel framework no longer explained how the fastest-growing products actually grow. The essay became foundational reading for growth teams worldwide.
Reforge didn't invent growth loops—viral loops, content loops, and paid loops existed. But Reforge systematized them into a unified framework, made them teachable, and positioned them as the successor to funnel-based growth thinking.
The AARRR Funnel Era (2007–2015). Dave McClure's AARRR funnel (Acquisition, Activation, Retention, Referral, Revenue) became the default framework for growth. It was linear: pour users in at the top, optimize each stage, measure drop-off. Funnels worked for understanding user journeys, but they didn't explain compounding growth.
The Rise of Product-Led Growth. By the mid-2010s, the fastest-growing companies—Dropbox, Slack, Airbnb, Pinterest—weren't growing through traditional funnels. They grew because users created more users. Dropbox users shared files. Slack users invited teammates. Airbnb hosts attracted guests. The product itself was the growth engine.
The Problem with Funnels. Funnels require constant input. Stop advertising, stop growing. But loops compound. One user creates multiple users who each create multiple users. That's exponential. Growth teams at companies like HubSpot (where Balfour was VP Growth) and Pinterest (where Winters led growth) were seeing this firsthand.
Reforge as Educational Platform. Brian Balfour founded Reforge in 2017 to systematize growth knowledge. Traditional business schools didn't teach modern growth tactics. Reforge brought together practitioners from the fastest-growing companies to share frameworks. Growth loops became the foundational mental model.
The 2019 Essay. "Growth Loops are the New Funnels" crystallized years of thinking. The essay explained why loops, not funnels, drive sustainable growth. It showed different loop types. It argued that growth strategy should focus on designing, optimizing, and sequencing loops. The piece went viral in the growth community.
The Racecar Framework. Later, Dan Hockenmaier and Lenny Rachitsky extended the concept with the Racecar Growth Framework: loops are the engine (self-sustaining), optimizations are lubricants (make loops run better), one-off tactics are turbo boosts (temporary acceleration), and inputs are fuel (what the engine requires). This made loops even more practical.
Adoption and Evolution. By 2020, growth loops had become the dominant framework at product-led growth companies. Growth teams mapped their loops, identified constraints, and sequenced new loops to maintain momentum. The framework replaced funnels as the primary mental model for sustainable growth. Every S-curve requires a new loop.