From Moon hotels to cattle herding: 8 startups investors chased at YC Demo Day
Investors have flocked to Y Combinator’s Demo Days for years to get their hands on promising startups building cool tech.
After all, the accelerator has produced some of the biggest tech companies in the world, from Airbnb and Reddit to Dropbox, Zapier and Stripe.
That’s why we make it a point to keep an eye on the event to spot the most interesting companies from each batch.
As I’ve been doing nearly every quarter now that the accelerator has moved to four cohorts a year, I asked nearly a dozen investors which startups were most in demand at Y Combinator’s Winter 2026 Demo Day earlier this week.
To ensure our list included truly sought-after standouts, a company had to be flagged as a ‘fave’ by at least two different venture capital investors to make the cut.
As for valuations, I’m hearing that at least a couple startups have raised funds at a $100 million price tag, though notably, those startups are already bringing in run-rate revenue of $1 million or more.
Even for the less buzzy startups not on this list, the “default” valuation this quarter seems to be around $30 million, which investors told me is roughly two-fold the current seed market average.
What it’s building: Deployable solar arrays for satellites.
Why it’s a fave: The startup claims it has developed solar arrays that are the size of a dining table at launch, but unfold to the size of a football field when they reach orbit.
The founders say their system can increase available power ten-fold while slashing costs by 88%.
Beyond Reach already has a flight planned for 2027, and says it has secured $325 million in letters of intent from leading space companies.
What it’s building: A ridiculously fast file transfer protocol.
Why it’s a fave: According to Byteport’s founder Jayram Palamadai, existing file transfer protocols like TCP are too slow for the AI age.
That’s why he built DART, short for Dynamic Accelerated Record Transfer, which can apparently transfer large files at an average of 10 times faster than TCP, and even up to 1,500 times faster on “reliable connections.” What it’s building: Continuous AI-powered security testing tools.
Why it’s a fave: To fight hackers using AI to launch non-stop cyberattacks, Hex is building AI agents that can act as penetration testers, constantly probing for vulnerabilities and security gaps in companies’ infrastructure.
