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Founder's guide to the Y Combinator interview
BY Justin Kan

Founders often wonder how to do well in their Y Combinator (YC) interview. YC has evolved into a well-oiled machine. More than 1,900 companies have gone through YC, giving the partner team a generous sample size to identify positive and negative traits in early-stage companies. You can’t get accepted into YC solely on the premise of your idea; you need to convince the partners that you are amazing founders who can build a large business.

There are a lot of technically-focused guides on YC interviews. Here are some basics.

1. Know what you’re doing

The most important outcome of your YC interview is to convince the interviewers that you are a great founding team. YC decides on the founders primarily on the confidence they project, and their expertise in their industry.

Know your business inside and out: You don’t need to know all the answers to every question, but you want to show that you’ve explored every pathway in the maze of your space. Balaji Srinivasan’s concept of “the idea maze” describes what you want to convey.

Know your core metrics: The core metrics can be whatever you think is important. But whatever you’ve selected, know them (and how they are changing daily, weekly or monthly) off the top of your head. Once you identify the metric that’s important, show that you have all the information around it. For example, if daily average users (DAU) is your main metric, be ready to discuss:

  • What is your DAU as of today?

  • How fast are you growing week-over-week? Month-over-month?

  • What actions are you taking to grow it? Homepage testing, funnel optimization, doubling down on a marketing channel?

Being able to drill down into your metrics helps you present a positive business case for investment (assuming the numbers are favorable). It also demonstrates that you are a data-driven founder who will build a company that stays focused on the numbers that matter—and constantly works to improve them.

When you don’t have metrics, it’s an early indicator that you won’t create an iterative feedback loop that will improve your startup systematically over time.

2. Understand the small and big idea

As Andrew Chen, General Partner at Andreessen Horowitz, accurately describes, startups have two major growth stages: zero-to-one, and one-to-n. Mastering each one requires an understanding of both the small and big idea. The small idea: To get off the ground, you want to show that you understand how to dominate your core niche. A narrative that describes how you encountered the problem, built it for yourself, then talked to 100 other people like you is tried and true for a reason: It shows that you are an expert in this problem space, you’ve done your homework and are now building a product with feedback from real customers. You should be able to convey the reasons why you’re going to attack — and dominate — a niche area with your product.

The big idea: But we all know that the end goal isn’t to own a very small niche, but to use that as a platform to successfully enter a much bigger arena. You’ll get asked about this, and better yet, you can actively guide the conversation in that direction.

What is the biggest idea you can convey on how this niche product grows into something huge? Expansion can happen in many ways, often by expanding geography, product category, or target customer. The important part is that you make a bold claim (that you believe) about how you will grow into something much bigger once you dominate your core niche.

3. Convey founder synergy

Your interview should be a demonstration of the great synergy on the founding team, and you don’t want to undermine that in any way. Beyond your in-person demeanor, you also want on-paper synergy. Partners look for a team that’s balanced. Having founders with complementary skill sets or areas of focus can be important. It’s completely fine if all founders come from a technical background, but one should be able to say “I’m focusing on operations” or “I’ll be in charge of marketing.”

If the founding team has worked together or has history, it’s also a good point to bring up. Not a necessity, but helps show that you have worked together and there’s one less unknown variable to worry about with your company.

How to prepare

Those are the most important aspects of your interview, but there’s much more you can do to set yourself up for success. Great YC interviews start weeks before you actually walk into the room to speak with partners.

It’s simple, and no one wants to hear it, but it helps to practice—a lot. Expose yourself to people who have been through interviews before, as this will reduce the chances that you’re thrown off by a stray question.

1. Find people who have done it

The YC ecosystem is big enough that there’s no excuse for failing to get help. A couple starting points:

  • YC network: Look through the list of all YC companies and identify anyone you know or could get an intro to.

  • Startup school: Go to the events or reach out to alums who offer to give free interviews.

  • Your own network: If you’re in any way involved in the startup community, ask for help. All it takes is one friend of a friend to get you started.

2. Talk to them

After you’ve connected with people who can help, ask them to interview you—or at the very least, send you questions. You’ll be surprised by the different types of questions that you otherwise wouldn’t have considered. That’s the point. Better to be taken aback in practice than in the real game.

3. Write out your answers

Write down all your answers as concisely as possible and rehearse, rehearse, rehearse. You don’t want to think on the fly. When you write down and repeatedly review your answers, they’ll be drilled into your head so deeply that you don’t have to worry about saying the wrong thing.

4. Practice the interview under extreme circumstances

Ask your friend or partner to dance in the background, or yell at you while you are reviewing answers—anything to try and throw off your focus. This is how you mimic the intensity of getting grilled by YC partners, some of whom you may have looked up to for years. Once you’ve prepared for the worst, the interview will feel tame by comparison.

Specific interview tips

You know the big picture and have practiced your answers—now it’s time for the real thing. Keep these guidelines in mind and bake them into your preparation.

1. Be concise: There’s a big difference in the perceived quality of a 25-second answer vs. a 45-second answer. Getting straight to the point—while making sure you cover all the important material—conveys confidence. More importantly, you need to maintain interest. You need to earn the partners’ attention, and the easiest way to do so is in direct, concise answers that don’t meander.

2. Convey your big three: The interview goes by in a blur, and you don’t want to walk out having left out a major selling point of your company. To prevent this, write down three important things that you must convey. If they don’t come up organically, guide the conversation in that direction.

3. Don’t get defensive: You’re being interviewed by people who have evaluated hundreds or thousands of startups. When you get defensive about a question, you’ll come across as someone who can’t process constructive criticism. Instead of being defensive, show that you’ve thought about it—or can do the homework to better answer it. A few weak answers can be passable, but defensiveness will be seen as a negative trait.

4. Have a lead speaker, but divide and conquer: One person on the team should take the lead on answering questions, but it’s hard for them to memorize every detail. Have a plan for handing off to certain team members on specific lines of questioning.

5. Don’t use jargon: Assume the YC partners don’t know all the acronyms and assumptions about your target market. Explain things to somebody who’s not an expert in your space—because more than likely, they aren’t. A good rule of thumb (and this applies to talking to any investor): you should be able to explain your product to someone who has zero industry context.

6. Be confident: It’s okay to be nervous, but don’t be nervous about being nervous. Remember that you’re the expert in your business. You know much more about the space than the partners interviewing you. Be confident in your answers, and walk into the room knowing that you understand this subject better than anyone else.

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