Slack

Klarna

Slack

Slack uses a freemium model. The free tier gives you access to your most recent 90 days of messages and 10 app integrations.

That's enough to get hooked. Then Slack charges per user per month — $8.75/month for Pro, $15/month for Business+, and custom pricing for Enterprise Grid.

The beauty of the model is that one person signs up, invites their team, the team gets addicted, and suddenly the company is paying for 500 seats. It's a virus that charges rent.

Klarna

Klarna makes money from merchant fees and consumer interest. Merchants pay Klarna 3-6% of each transaction — they're willing to pay because Klarna increases conversion rates by 30%+ and average order values by 45%.

On "Pay in 4" (interest-free installments), Klarna makes money purely from merchant fees. On longer financing (6-36 months), Klarna charges consumers interest up to 25% APR.

Klarna also earns revenue from its shopping app (affiliate commissions when users discover and buy from merchants), and from its Klarna Card.

Slack

Stewart Butterfield had already done this exact thing once before. In 2002, he was building a massively multiplayer online game called Game Neverending.

The game flopped but one of its features — a photo-sharing tool — became Flickr, which Yahoo bought for $35 million in 2005.

So in 2009, Butterfield did it again. He started a company called Tiny Speck to build another game called Glitch — a quirky, non-violent MMO where players collaborated instead of fighting.

The game was beautiful, weird, and a complete commercial failure. It shut down in November 2012 after never finding a big enough audience.

But the internal communication tool the Glitch team had built for themselves was something special. They had created a searchable, organized messaging system because email was driving them insane.

Every conversation was in channels. Everything was searchable.

Files were shared inline. It was everything email should have been but wasn't.

Butterfield looked at this internal tool and thought: this is the actual product. In August 2013, Slack launched in preview.

Within 24 hours, 8,000 companies had signed up. Within two weeks, it was 15,000.

The growth was so fast that Butterfield said it felt like "trying to drink from a fire hose."

Klarna

Sebastian Siemiatkowski, Niklas Adalberth, and Victor Jacobsson were students at the Stockholm School of Economics. In 2005, they entered a startup competition with an idea: let people buy things online and pay later.

At the time, online shopping was still new and most people were terrified of entering their credit card details on the internet. The idea was simple — Klarna would pay the merchant immediately, and the customer would get an invoice with 14-30 days to pay.

The competition judges hated it. The idea was dismissed as financially irresponsible and the team didn't win.

But Siemiatkowski pressed on. Swedish e-commerce was growing fast and merchants were desperate for any way to reduce cart abandonment.

Klarna's "pay after delivery" model was a hit because it shifted the risk — customers could receive the product, try it on, and only pay for what they kept.

The first customers were Swedish e-commerce merchants selling fashion and home goods. Klarna handled the invoicing, fraud detection, and collections.

Merchants saw conversion rates jump because customers were more willing to buy when they didn't have to pay immediately.

Slack

Slack grew almost entirely bottom-up. Nobody sold Slack to companies.

Employees adopted it on their own and then convinced their bosses to pay for it. One developer would start using the free version, invite their team, and within weeks the whole department was hooked.

IT departments would discover that half the company was already on Slack before anyone asked for approval.

The integrations strategy was genius. Slack made it dead simple for other software tools to plug into Slack.

Instead of checking Jira for bug reports, Salesforce for deals, and GitHub for code changes, everything pushed notifications into Slack. Slack became the operating system of work — the one app you kept open all day.

Word of mouth was the main growth driver. Slack didn't spend heavily on advertising early on.

They spent on making the product feel delightful. The loading messages were funny.

The emoji reactions were addictive. The search actually worked.

People genuinely liked using it, which is almost unheard of for enterprise software.

Klarna

Klarna grew by being embedded at checkout. The strategy was to sign up the biggest online retailers and become a payment option alongside Visa and PayPal.

Once Klarna was at checkout, consumers discovered it organically. The "Pay in 4" button became ubiquitous across fashion, electronics, and home goods retailers.

The Klarna app became a growth engine beyond checkout. By building a shopping app where users could browse products, discover deals, and track deliveries, Klarna turned from a payment method into a shopping destination.

The app has 35+ million monthly active users who start their shopping journey inside Klarna before even visiting a retailer.

International expansion was aggressive. Starting in Sweden, Klarna rolled out across Europe, then into the US, UK, and Australia.

The US became the biggest growth market — American consumers were especially receptive to Pay in 4 as an alternative to credit cards. By 2023, Klarna had 34 million US users.

Slack

Microsoft Teams was the existential threat. When Microsoft bundled Teams for free with Office 365 in 2017, Slack knew it was in trouble.

Microsoft had 300 million Office users who could start using Teams without paying anything extra. Slack even took out a full-page newspaper ad welcoming Microsoft to the chat market — a bravado move that masked genuine fear.

By 2020, Teams had overtaken Slack in daily active users purely on distribution.

The pandemic was a double-edged sword. Remote work exploded demand for Slack, but it also exploded demand for Teams, Zoom, and every other collaboration tool.

Slack's growth accelerated but so did everyone else's. The window where Slack was the obvious default was closing.

Revenue growth started slowing. After years of 50%+ annual growth, Slack's growth rate dropped to the low 30s by 2020.

Wall Street punished the stock, which dropped from its IPO price. The writing was on the wall — Slack couldn't outrun Microsoft alone.

In December 2020, Salesforce announced it was acquiring Slack for $27.7 billion. Butterfield stayed on as CEO until 2023, then left.

Klarna

The valuation collapse was humiliating. Klarna raised at a $46 billion valuation from SoftBank in 2021.

One year later, they raised a down round at $6.7 billion — an 85% haircut. It was the most dramatic valuation drop in fintech history.

Employee stock options were underwater. Siemiatkowski had to lay off 10% of the workforce.

The entire BNPL category went from hot to radioactive in months.

Credit losses are the existential risk. Klarna is lending money to consumers who want to buy things they can't afford to pay for right now.

When the economy slows, defaults rise. Klarna's credit losses hit $1 billion in 2022.

The company had to tighten underwriting significantly and pull back from riskier markets. The tension between growth (approve more loans) and profitability (reject risky borrowers) defines every quarter.

The IPO in 2025 was a comeback story but with caveats. Klarna went public at $15 billion — a major recovery from the $6.7 billion trough but still less than a third of its 2021 peak.

The company finally turned profitable by slashing costs with AI (replacing hundreds of customer service agents with AI chatbots) and tightening credit standards. But investors remain cautious about the BNPL model's long-term sustainability.

Slack

Slack is the core messaging platform — channels for teams, direct messages, threads for focused discussion, and huddles for quick voice/video calls. Slack Connect lets you message people at other companies directly through Slack instead of email.

Slack Canvas is a built-in document editor for notes and wikis right inside channels. Workflow Builder lets non-technical users automate repetitive tasks without writing code.

The App Directory has 2,600+ integrations — connect Google Drive, Salesforce, Jira, GitHub, or basically any tool your company uses.

Klarna

Pay in 4 is the signature product — split any purchase into four interest-free payments over six weeks. Pay in 30 lets customers receive the product first and pay within 30 days.

Financing offers longer-term payment plans with interest for larger purchases. The Klarna App is a shopping destination — browse deals, track orders, manage payments, and earn cashback.

The Klarna Card is a physical Visa card that lets users Pay in 4 anywhere. Klarna Creator is a platform for influencers to earn commissions sharing products.

Klarna AI is their customer service chatbot that handles two-thirds of support queries.

Slack

Accel Partners, Andreessen Horowitz, Social Capital, GV (Google Ventures), SoftBank, Dragoneer Investment Group

Klarna

Sequoia Capital, SoftBank, Silver Lake, GIC, Atomico, Commonwealth Bank of Australia, Heartland