@duolingo co-founder and CTO.

Joined March 2009
33 Photos and videos
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Thanks to @HarryStebbings at @20vcFund for sitting down with me to talk about (almost) everything. You can listen to the episode on Spotify now:  open.spotify.com/episode/5ij… Here’s just a few of the topics we covered:
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Is the generation born today called GenAI?
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Never leave the terminal
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Severin Hacker retweeted
It's so weird how difficult it is for the left to understand that all you have to do to decrease housing costs is to let people build more housing.
For 45 years, Berkeley built virtually no new housing. By the mid-2010s, it was the most expensive college town in America. Shortly thereafter, YIMBYs took over and kicked off a building boom. Today, nominal rents are below 2018 rates—remarkable progress on affordability.
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Severin Hacker retweeted
excited to share what we have been up to. your iphone’s home screen hasn’t changed in ~20 years. it’s the same static grid of icons since launch with zero awareness of your actual life. @skye is a new agentic home screen for iphone. no telegram. no mac mini. & no claws required. skye is ambient intelligence that just works. it continuously listens to your context & acts on it. it builds your reading lists, gives you personalized weather, drafts email replies, prepares you for meetings & trips, flags suspicious charges, works through your reminders, tracks your health, & gives you one tap intel on wherever you are (restaurants, museums, neighborhoods, etc). all surfaced on your home screen. over the next few posts i’ll break down how it works, why we built it, & why we think it deserves to exist in the world. beta starts today. if you’re on the list, you’ll get access very soon. app store shortly after. deeply appreciate you all following along on this fun little journey. also please join our discord !
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Unpopular opinion: The most dangerous thing on the road right now is a human holding a steering wheel.
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You can separate the world into those who have used Claude Code and/or OpenClaw in the last few weeks, and everyone else.
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Why is there no American coffee? We accept the "coffee belt" as law. I don't. I am funding research at UF to use genomics to make coffee thrive in Florida. Let's grow the impossible. @lfelipeferrao
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Severin Hacker retweeted
You have 19 days to learn Spanish for Bad Bunny's halftime show, don't disappoint me.
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The second best feature of a mechanical watch is the lack of notifications.
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I did not expect this to go viral.
Should you get a PhD in CS/AI? Both seem to be true: 1. 95% of PhDs would have done equally well career-wise without one. 2. 95% of real AI breakthroughs (ImageNet, Transformers) came from PhDs.
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Should you get a PhD in CS/AI? Both seem to be true: 1. 95% of PhDs would have done equally well career-wise without one. 2. 95% of real AI breakthroughs (ImageNet, Transformers) came from PhDs.
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A belief I hold: 1 book every 2 months, 5% retention, 1 idea implemented in real life. That will make you outperform 95% of your peers. It has to be a book, not a thread or a podcast.
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Severin Hacker retweeted
Replying to @KarelMercx
Duolingo served its purpose and I am thankful for @LuisvonAhn @severinhacker . By spending 45 mins on it daily in the morning (anywhere), I am able to converse in Indonesian in a casual setting. That was my intent, to do that w my friends and specific individuals.
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Severin Hacker retweeted
7 Nov 2025
lost my streak and now i’m spiraling
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I’ve been using tonal for 3 years. Underrated product.
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At @duolingo, part of our “secret sauce” is our home-built analytics and experimentation platform. The PMs and Engineers we’ve hired from well-established tech companies (i.e. Google, Spotify, Meta) often say it’s the best they’ve seen. This platform allows us to test, learn, and scale ideas faster than anyone else in the consumer mobile space. Most importantly, it helps us move at super-speed towards our goal of making learning both effective and delightful for millions of learners.
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Pretty sure I spent half my life vitamin D deficient because of high latitude winters.
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The Startup of You by Reid Hoffman & Ben Casnocha is the book I recommend THE most when people ask for career advice. Underrated, practical, and right. After 32 you should never have to apply to jobs again. Your network should bring every opportunity.
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