How does YC define a promising startup? What qualities in founding teams do they value most?

To get noticed by Y Combinator (YC), you need to understand the game they're playing. They aren't looking for a perfect business plan, but rather a few more fundamental things.

Regarding "promising startups," they primarily look at three points:

1. A Real, Painful Problem: Are you solving a real, existing problem that causes significant headaches for many people? Ideally, you yourself are a victim of this problem, which is called "scratching your own itch." Because only by personally experiencing the pain will you truly understand what users need and be most motivated to solve it. A "vitamin" product that's nice to have is far less appealing than a "painkiller" product that's essential.

2. A Huge Market: Does what you're doing have a high ceiling? YC invests in companies that can become multi-billion or even tens of billions of dollars in valuation; they need "home runs." Therefore, the market corresponding to the problem you're solving must be very large. To put it metaphorically, they want you to be fishing in a vast ocean, not a small pond. Even if you're currently only serving a small group of early users, they must be able to see that this group connects to a huge potential audience.

3. Early Traction: Have you already built something? This doesn't necessarily mean revenue. It could be a very rough Minimum Viable Product (MVP), a growing waitlist of users, or a dozen loyal users who use your product daily even if they're not paying. The key is to prove that you're not just a "thinker" but a "doer." YC strongly believes in "doing things that don't scale," such as manually inviting your first 100 users and talking to each of them. These clumsy but effective actions are the best evidence that people want your product.

Regarding the "team qualities" they value most, people always come first:

Ultimately, YC invests in people, not ideas, because ideas always change, but a great team can navigate any change.

1. Founder-Market Fit: Simply put, are you the "chosen one" to do this? Do your past experiences, skills, or deep insights give you an advantage over others in solving this problem? For example, an experienced game developer building a new game engine is much more reliable than a financial analyst doing the same.

2. Bias to Action & Rapid Iteration: This is something YC values extremely highly. They like "doers" and dislike "talkers." Can you quickly release a new version within a week based on user feedback? How fast is your execution from idea to product? In the YC accelerator, the sole goal each week is "growth," which is driven by the team's incredible execution.

3. Resilience / Grit: Starting a company is a trial; 99% of the time, you'll be hit by various problems. YC looks for teams that, no matter what difficulties they encounter, can find a way to survive and keep moving forward. They call this quality "being a cockroach." In interviews, they will assess whether you possess this quality by asking about your past experiences overcoming significant challenges.

4. Clear Communication & Strong Founder Relationship: If it's a team, the relationship between the founders is crucial. Countless startups die due to founder conflicts. Is your communication honest and efficient? Do you have a strong bond that allows you to weather the toughest times together? YC interviewers will observe your interactions when answering questions to determine if your relationship is healthy.

In summary, YC's ideal profile is: a founder (or a group of founders) who deeply feels the pain of a problem, possesses cockroach-like resilience, and has explosive execution power. They are operating in a huge market and have already, with even a rough product, initially validated that people truly need it.