Case study: Slack, the fastest-growing business app in history (Part 1)

Updated on October 18, 2026: figures reviewed and updated.

Case study: Slack, the fastest-growing business app in history

Slack has entered Silicon Valley’s hall of fame as the fastest-growing business app ever, and the Slack growth strategy behind that record is worth studying closely. Since its public launch in February 2014, Slack has racked up achievements such as:

• 8 million daily active users, more than 3 million of them paying (May 2018)
• The highest conversion rate (30%) of any freemium software product
• Used and paid for by 65% of Fortune 100 companies (May 2018)
• A valuation of USD 7.1 billion in August 2018

These numbers are truly remarkable when you consider that Slack grew from USD 0 to USD 7 billion in less than 5 years. What is even more impressive is that the Slack app was born out of earlier business ventures that had failed.

Every success story has done three things over the course of its life cycle:

• Product-market fit: the right idea at the right time
• Rapid growth: scaling at an extraordinary pace
• Reinforcement: a built-to-last model

In this growth study, we will look together at the story of Slack, at its early and most fundamental strategy for taking over the world, and at how it built a platform that helped change the way people communicate at the office.

Founder and CEO Stewart Butterfield was no stranger to fast-growing apps. He had already built Flickr about 10 years before he started Slack.

Stewart, who was born and raised in rural British Columbia, had no real exposure to technology at all until he went to university in the late 1990s, where he became fascinated by the school’s Unix machine and by how Unix could be used to create something beyond lines of code.

After getting out of the dot-com bubble in 2000 with USD 35,000 in severance pay from an e-commerce job, he started building a web-based game called Game Neverending. With its crude graphics and its small but passionate community, the game is what sparked Stewart’s love of design and communication.

The game could not raise any investment, and that made it hard to scale. Even so, a small team built technology that let users tag photos with other users, well before Facebook and Instagram offered that feature to anyone.

Meanwhile, Stewart’s USD 35,000 was steadily running out, and the game was edging closer and closer to failure. Under pressure from their shrinking finances, Stewart and his fellow tech-loving colleagues took the core technology that made the game unique, the ability to share and tag photos, and put it to another use.

After that, he started on Flickr, and with some help from Google, the team began picking up users at a fast pace. At the time, Google had just bought Blogger, a CMS platform that let anyone create a website. But because you could not host images on Blogger, Google directed users to store their images on Flickr.

The Flickr team was not profitable, and its server hosting costs were very high, but Flickr caught the attention of Silicon Valley giants Yahoo! and Google. Yahoo! offered the Flickr team USD 20 million, and the 8-person team became millionaires overnight. But instead of keeping its culture of fast iteration and a flexible workplace, the team found that Yahoo!’s 11,000 employees slowed down its startup-style decision making.

After three years, once their shares had fully vested, Stewart brought back his core people and returned to his original project: another web-based multiplayer game, this one called Glitch. Since they were now well known for the success of Flickr, the team had more time on its side and found it much easier to attract investors. They raised USD 17 million, which went into new hires (mostly people working on graphics), and the Flickr name meant the game attracted a lot of users.

But there was a big problem, the one that sinks most startups: a leaky bucket.

Although users found the game and tried it, 99% of them never came back, because it did not feel meaningful and was too abstract. Stewart had let a lot of people down and the project was slowly hitting a dead end, so he made the hard decision to pull the plug in 2012.

Chapter 1: Team cohesion and perfect timing

From a business point of view, Glitch was a disaster. Along the way, however, the team had developed an internal communication system that helped it reach a remarkable level of productivity at work.

The platform was built around the concept of channels, which let team members chat with each other directly or within a specific channel. Glitch stored all communication and was an alternative to the typical way offices communicate: email. With email, team members have no context, because 99% of messages are invisible to you unless you are CC’d.

The Glitch team did not realize how useful the communication system they had built really was until they shut the company down. It was far better than communicating by email, and they never wanted to go back to working without a system like it. Maybe other people would like the way of communicating that Glitch made possible, too.

After Glitch closed, Stewart was left with only his core people, the same group that had stuck with him since the days of building Flickr and the game. By that point, they had been working together for almost 10 years and genuinely enjoyed building products together. On top of that, the hard times they had been through had bonded the whole team even more closely.

Just weeks after Glitch shut down, Stewart and his team started working on the Slack app. Within a few months, they had rebuilt the entire internal communication system from the ground up.

Solving the problem of getting messages through

Internal communication is a problem for most companies, even if they do not necessarily know that it is. As more and more software startups scale quickly, they discover that internal communication breaks down when a team of a handful of people grows to 20, 50 or more than 100 people within 1 year.

Slack happened to be in the right place at exactly the right time.

Slack was not the first new communication system: apps such as Yammer, Campfire and HipChat already had small but loyal user bases. Seeing that copycats kept appearing without end, Slack knew that to succeed it had to solve the communication problem better than all of the others.

What worked in its favor was a huge Total Addressable Market (TAM): companies of every size, from small startups to large enterprises, need a tool like this.

Slack’s core features and capabilities are:

• Segmented, contextually relevant communication, including persistent chat, direct messages, and voice or video calls within and between teams
• Synced communication and collaboration across multiple devices and platforms
• Integrations with third-party apps and legacy enterprise software, as well as apps and chatbots custom-built for Slack
• Customizable notifications and advanced search across everything in Slack

Although the TAM was much the same for every existing competitor, Slack set itself apart with a brand that was fun, easy to use and centered on the customer. Combine that with an excellent product launch, and Slack ended up with the edge in market share.

Why did Yammer fail?

Microsoft’s Yammer (now Viva Engage) was basically solving the same problems as Slack, but its approach did not work. Although 80% of customer teams had started using Yammer, senior staff were not willing to try it.

You also had to use Microsoft Office 365 to access Yammer. Many potential users were already using Google Docs (especially when they needed to collaborate). Microsoft Office 365 required users to pay and commit to terms, while Slack and Google Drive were free.

Slack was able to overcome people’s reluctance to adopt it with a fun interface (see Chapter 4), an attractive freemium model (see Chapter 5) and an easy-to-use platform that let everyone get value from it (see Chapter 6).

Why emerging markets matter

Slack’s original team was made up of 4 core members: Stewart Butterfield, Eric Costello, Cal Henderson and Serguei Mourachov.

The team communication system they had developed during their time at Flickr and Glitch helped them work more efficiently, and they also noticed that the productivity of everyone else in the company had gone up.

Everyone who worked with the core team saw how effective their system was, and when those people moved on to other companies, they quickly noticed the inefficiency that “proto-Slack” had been solving. The core team knew what they were doing; they already had the market validation they needed.

The lesson here is that emerging markets are a great place to launch a new product, especially once you have validated the market. Work with people who are the best at what they do, and you will probably know how to handle the pressure that comes with a fast-changing startup. Competition is a good sign that you are heading in the right direction, but launching a product into a competitive market means you have to create an outstanding product and serve your customer base better than anyone else.

Chapter 2: Executing the perfect launch

If you are running a startup, the odds are stacked against you and you will face a lot of difficulties.

You need to find the pain point, solve the problem behind it and earn your customers’ trust. If your product hypothesis turns out to be wrong, you have to go through the testing process again, as long as you still have budget left.

Slack knew it had a solution to a real business pain point. Thanks to its earlier success, the team was able to raise venture capital and put its focus on a product launch that was both strategic and distinctive.

Instead of a “growth hack”, the Slack team combined the work of product design agency MetaLab, the reputation they had built from the success of Flickr, and PR agencies to come up with Slack’s distinctive hook: “The Email Killer”.

Slack’s intention was never to replace email, as Stewart Butterfield himself said:

“Email has a lot of benefits: it is the basic form of communication for formal exchanges. But email is not a very good way to manage internal communication.”

The preview version gave Slack a chance to test its core features while building relevance around a small set of chosen features. (Note that Slack deliberately did not call its pre-launch version a “beta”. From the user’s point of view, the difference in perception is huge. In a beta, users are there to test everything to help the company. But if users are in a “preview”, they are part of a select few who get to use the product before anyone else and enjoy the privilege of being first. Imagine how it would look if Tesla or Apple unveiled a half-tested product.)

They launched the Slack “preview” so the team could:

• Fix bugs and major errors
• Identify the features and benefits that resonated with the market
• Activate an early user base to champion Slack through word of mouth

Once those problems were fixed, the team was ready to take Slack all the way to its product launch.

Hiring an outside firm to build the brand may well have been the only option open to Slack at the time. Bill Macaitis did not step into the CMO role until November 2014, which meant Slack relied entirely on a third-party agency to create the look of its brand. Outsourcing a whole function and depending on a third party is an exercise in trust and faith.

Luckily for Slack, the move paid off with the best result it could have hoped for.

It took many months of careful planning and coordination across every channel, but as soon as the product hit the market, Slack went viral.

Slack already had several advantages before its official launch:

• Testimonials collected from companies and displayed on its landing page
• Twitter used to show off a “Wall of Love”: tweets from users singing its praises
• A PR firm used to reach almost every relevant online and offline tech publication:
  • Fast Company: Flickr Co-founders Launch Slack, The Email Killer
  • TechCrunch: Slack, Flickr Co-Founder Butterfield’s Business Collaboration App, Exits Beta With Premium Plans
  • The Verge: Slack is winning out over email
  • VentureBeat: Flickr co-founder sends “email killer” Slack out into the world
  • Inc.com: Why Slack is beating email once and for all

Slack tested its product-market fit to work out how best to attract new users. It then used PR agencies, armed with a distinctive angle, to win over users right away. PR agencies are usually expensive, but Slack knew they were the perfect way to reach as many people as possible in a short time (you can do this by pitching reporters yourself, but it takes much longer because you have to build the relationships first).

Building social proof through the Twitter Wall of Love created social credit, and having the “email killer” headline picked up by widely respected publishers such as The Verge, TechCrunch and VentureBeat brought in unique traffic.

Slack’s Wall of Love

Whenever a Twitter account posts something or retweets someone else, that post shows up on the account’s timeline. Slack created a kind of archive that stored every positive tweet whenever Slack was mentioned in one. The result was a giant wall of positivity and love, which they named the “Wall of Love”. The Wall of Love is a separate Twitter account that collects all the nice things people say.

Slack paired this with a traditional marketing channel: advertising in the Wall Street Journal

What made the Wall of Love work?

• Peer-to-peer social credit. Potential Slack users trust testimonials from their peers more than claims on a website or dry corporate testimonials.
• Brand building and relationship building through open, transparent two-way conversations, which let Slack find out what its users really wanted.
• Based on what fans wrote, Slack could put together a library of information on how to solve the problems new users ran into.
• Slack turned its users into content creators. New, user-generated content fed a network effect, because every Twitter user has their own social connections through their followers.
• The Wall of Love was unique and fresh (at the time). It generated and surfaced new posts, which drove huge amounts of traffic to the website.

A closer look at the brand’s core values

Keep in mind that most of Slack’s audience was companies from Silicon Valley, a place where a great deal of conversation happens on Twitter.

Great brands are built on solid foundations: a strong team with a proven, thoroughly tested track record; a clear value proposition and a product that has been validated and fits its market; a customer-centered company culture and a solid brand. If we borrow the term MVB (Minimal Viable Branding), we can break Slack’s brand down into its individual elements.

MVB is a concept adapted by Scott Kraft, Denise Lee Yon, Tino Chow and Madeline Gerber to build a brand image that the public can easily recognize, and to lay the groundwork for a company’s culture and for how it communicates in-house and outbound.

According to Kraft, MVB consists of:

• Brand pillars: 1 to 3 adjectives that represent the company
• Audience needs: what the audience needs to know
• Functional needs: the benefits, spelled out
• Emotional needs: how the audience sees the brand at each emotional level
• Brand personality
• Promise
• Company vision

At its core, MVB works as a blueprint for the product, one that carries the promise of what the company will deliver to its customers in the future.

Slack’s brand personality is made up of:

Brand pillars + target audience + their top 3 needs + top 3 emotional benefits

For Slack, this means:

• Brand pillars: Fun, Inclusive, Connected
• Target audience: Employees who struggle with communication inside their company
• Top 3 needs: A more efficient way to reach the rest of the team, faster responses, timely information

If we describe Slack as a brand through the three other elements of MVB:

• Personality: Fun, connected, diverse
• Promise: Connect everyone in-house with a simple but powerful system for team communication
• Vision: Make work happen

Whenever you see Slack content, you should be able to connect these values and elements to its brand. As you dig deeper, you find that this mindset has been built into the thinking of every member of the company, all the way up to the board.

The lesson here is not to overlook the power of traditional marketing. Create hype, and use a strong message that pushes people to share your posts again and again. Slack’s message was “The email killer”: a controversial claim that also addressed a painful problem.

Chapter 3: Branding is everything in the Slack growth strategy

A brand is the launchpad from which success takes off. Slack hired MetaLab, a firm that specializes in designing successful products, to turn its original prototype into a polished product.

Design and experience

Most well-known enterprise software is big, boring and lifeless. If you compare Slack with HipChat (Slack’s main competitor at the time), you can easily tell which of the two looks more fun to use.

Andrew Wilkinson of MetaLab said of Slack: “We gave Slack the color scheme of a video game, not an enterprise collaboration product.”

With a design that was recognizable, fun and easy to use, Slack stood in sharp contrast to the other competitors of its time.

Different types of marketing

Using content that serves each role at the top, middle and bottom of the funnel along the customer journey, Slack chose to create content not only in text but also in visual and audio formats.

“Animal!”, a product video, became hugely popular:

“Animal!” was a project that cost the company USD 1 million. The directors, Alan Smith and Adam Foulkes, went through an onboarding process (“Slackification”) similar to the one users go through, so they could convey the brand message accurately in the video.

The animals in the video are all very different (a lion, a dolphin, a rabbit, a sloth, an owl, a beaver and so on), but they manage to complete a complex project by communicating effectively.

Slack’s first podcast was “The Variety Pack”, produced by Pacific Content and launched in May 2015. By the end of that year, they had published 17 episodes and passed 3 million listens, in a biweekly format with half-hour episodes.

The podcast topics were not specific to Slack itself but reflected the interests of Slack’s users: career changes, workplace lifestyle, the future of work and so on. The podcast also had a light-hearted tone that showed Slack’s commitment to making work fun. The Pacific Content team worked with Slack to produce 28 episodes of the Slack Variety Pack, released every 2 weeks in half-hour episodes to engage Slack’s audience.

Bill Macaitis, Slack’s former CMO, said:

“Although podcasts are becoming more popular, if you are a podcast listener, there is a good chance you are also an early adopter. So this is one way to help us spread the word about Slack widely.”

Slack worked closely with producer Steve Pratt of Pacific Content, giving its feedback on every single episode. The focus was on telling compelling stories with small slogans woven in, such as “Slack: Love What You Do” and “Slack: Make Work Less Work-y”. In the end, the podcast reached a large audience at a fairly low cost.

Because “a brand is the sum of all the touchpoints a customer has with you” and Slack relied mainly on word-of-mouth marketing, its well-known Wall of Love Twitter account collected and displayed every kind thing people tweeted about it

Stewart Butterfield added: “Every customer interaction is a marketing opportunity. If you go above and beyond on customer service, people are much more likely to recommend you.”

Localization is more than translation

In today’s highly segmented market, a one-size-fits-all approach is not a good way to communicate with users. You do not just copy and apply a business model; you have to adapt to the market you are moving into. In other words, localization is more than simple translation.

Working from NPS (Net Promoter Score) data, a measure of customer satisfaction, the marketers on Slack’s Global Team look at the growth rate and activation rate of new customer groups. It is important for them to know whether the people who sign up for Slack go on to keep using it. In a market this large, segmenting your audience and making a solid plan to win over the places where new customers are is very important.

For that reason, Slack chose a localized approach for each market instead of taking one broad approach across most of its markets.

Chapter 4: Customer experience as the North Star

Slack was able to enjoy extraordinary growth without any marketing staff at all. As Josh Constine of TechCrunch once put it:

“Slack’s growth rate is unprecedented. Both Slack’s daily users and its paid seats grew 3.5 times in just one year.”

As mentioned earlier, Bill Macaitis, previously CMO at Zendesk and Senior Vice President at Salesforce, credited the growth rate as of November 2014, 9 months after the public release, as extraordinary. Instead of relying on growth hacks, paid marketing channels and short-term tactics, Bill Macaitis focused on one single thing: creating a customer experience that people love.

Andrew Chen, former Head of Rider Growth at Uber and a marketing leader, talks about the law of declining clickthrough rates, a trap many companies fall into: any marketing channel that worked like “gangbusters” in the past eventually stops delivering the same positive ROI over time. Put another way: every marketing channel has its day, and sooner or later it becomes outdated.

If you can reach the point where people keep recommending you to their friends and colleagues, you are on the path to real growth. Once people had tried Slack, they felt they had to tell others about it. Stewart Butterfield on the word-of-mouth effect of Slack:

“Unlike any enterprise software before it, people talk about Slack. They post on Twitter and say: I recommend Slack. And you know, nobody says that about software they have to use at work.”

Y Combinator CEO Sam Altman’s mantra is: “Customer love is all you need. 100 people who love your product are better than 1 million people who like it.”

HubSpot founder Dharmesh Shah would never trade customer happiness for short-term gains. As he puts it: “Chasing growth at a frantic pace comes at the cost of a mortgage on customer happiness.”

Bill Macaitis, Slack’s CMO, explained that “a brand is the sum of every experience [customers] have with you.”

Slack embraced that philosophy fully:

• Fast, frictionless onboarding: It takes just three clicks to start using Slack.
• Fair pricing: Members who have not used Slack for more than 28 days are not charged, and any amount already paid is added back as credit
• Customer success: Every new hire goes through a 9-week training program so they fit in, adapt to the company culture and learn to communicate the Slack way.

The lesson here is “dare to be different”, but never underestimate functionality and the best possible customer experience. Word of mouth equals growth.

(To be continued)

This article was compiled by Adtek, drawing on original content from Single Grain (2019). Updated on October 18, 2026.