Clef

In 2011, Brennan Byrne was working at Adobe on the Strategic Alliances team, trying to prove the company could track users on mobile devices without Flash. Around the same time, LinkedIn suffered the largest password breach in history at that point. Brennan realized that developers had abandoned passwords for secure logins years ago, using cryptography-based methods like SSH instead. The obvious solution was to bring that same technology to everyday users through their mobile phones. "I kept thinking like, oh, the next iPhone will let me use it to login to my Mac, but it kept not happening," he recalled. "And so I decided to build it."

Brennan started tinkering with the idea alongside co-founder Mark, later convincing engineer Jesse to join the team. Unlike many startups chasing big rounds immediately, they raised $150-175K from friends and family to cover basic expenses: founder salaries, server costs, a small office, and some PR work. "Almost entirely food and lodgings for founders," Brennan explained. The three co-founders kept their heads down for two years, focusing obsessively on product quality before hiring their first full-time employee. They built Clef to work exactly like SSH—using cryptographic key handshakes instead of passwords, so Clef's database would contain nothing valuable if breached, and login messages couldn't be exploited if intercepted.

Clef faced a classic two-sided market chicken-and-egg problem: websites wouldn't adopt it without users, but users wouldn't install an app with nowhere to log in. They tried various tactics to bootstrap growth, but the real breakthrough came in late 2013 when the New York Times published a flattering piece calling the experience "magical." Interestingly, the article didn't immediately spike signups—instead, it took about a month for the credibility to sink in. "What happened was all of a sudden we had credibility," Brennan said. "We had gone from this weird goofy thing to something trustworthy. We weren't like a fly by night organization anymore."

Once the New York Times article gave them credibility, word-of-mouth took over. The team deliberately avoided trying to "boil the ocean" and instead focused on deep penetration within specific user communities. Their strategy was to find clusters of websites serving the same users, get Clef adopted across all of them, and create "incredibly loyal fans" for whom the tool became pervasive rather than a one-off novelty. By the end of 2014, they had grown to over 124,000 websites using Clef and closed their seed round. Growth remained steady through 2014 as they attended events, built relationships, and listened obsessively to user feedback.

But success brought new challenges. A website in Hong Kong crashed when Clef's users flooded it after a promotional email, leaving the company responsible for the fallout. Switching between user communities required relearning everything, turning the metaphor of "pushing a boulder uphill" into one of "chasing a rolling boulder while also needing to push it again." By the time of this interview, the team had grown to 8 people.

With $3.1M raised and 124,000+ websites using the platform, Clef had become a serious player in passwordless authentication. But Brennan's impact extended beyond the product. At just 24 years old, he invested significant time building an intentional company culture and open-sourcing Clef's employee handbook—a rare move for startups. He worked with HR lawyers and consulted respected founders to create policies on hiring, compensation, and workplace practices, then published everything publicly because other founders kept asking to see it. The handbook became a hiring differentiator: candidates were drawn to a startup with transparent, thoughtful practices. "It's been really hard to correct later in a company's history," he explained about culture-building. "I want to do it right from the start."