How Y Combinator works

Each quarter, more than 10,000 companies apply to Y Combinator. YC usually accepts approximately 1% of them. Each company that YC accepts receives $500,000, three months of advice, and one day in front of a large room of investors. What does YC want from a company, and what do the founders do in those three months? This lesson shows the path of one application, from the form to Demo Day.

What an accelerator is

An accelerator is a short program for very young companies. It gives you three things:

• Money, in return for a part of your company
• Advice from partners and from other founders, for a fixed period
• An audience of investors at the end, at an event called Demo Day

Y Combinator (YC) is the best-known accelerator in the United States. It invests $500,000 in each company that it accepts. The program is three months long, in San Francisco, and a new group of companies starts four times each year. YC also made the SAFE in 2013. The lesson on the YC deal shows what YC’s $500,000 buys.

Four batches each year

YC puts the companies that start together into a batch. Each batch has a code: a letter for the season and two digits for the year. W26 is Winter 2026, S26 is Summer 2026, and F26 is Fall 2026. The YC directory writes Spring 2026 as P26, but YC wrote Spring 2025 as X25.

The number of batches changed through the years:

• From 2006 to 2023, YC had two batches each year, Winter and Summer.
• In 2024, YC added the first Fall batch (F24), for three batches.
• From 2025, YC has four batches, with the first Spring batch (X25).

With four batches, the next batch is never more than approximately three months away. At this time, you can also apply to the batches after the next one. Thus a founder who is not ready this season does not have to wait a year.

At the time of this lesson, YC accepts applications for Winter 2027 (W27). The on-time deadline was November 2, 2026, at 8 p.m. Pacific time, and YC still accepts late applications. Founders who applied on time get a decision by December 11, 2026. The batch is from January to March 2027 in San Francisco.

The application

The application has two parts: a written form and a video. The video is one minute long, and only the founders appear in it. YC wants to hear the founders speak in their own words. Thus the video has no demo and no written script.

Many founders think that they must have revenue before they apply. The YC FAQ does not agree. Make a guess before you read the answer.

Predict first

On average, what part of the companies in a YC batch are just an idea, with no product yet?

Type a guess before you continue. A guess first, even a wrong one, makes the answer easier to remember.

Your guessSave my guess

YC examines the team carefully. The FAQ says that the founders must have the skills to build the product themselves, not pay an outside company to build it. YC partner Dalton Caldwell gave a number in a 2023 talk. A team gets “five times better odds” of an interview if one founder can get a technical job at a top YC company.

Two more facts from the FAQ are important:

• An introduction is not necessary. YC says that it does not rely on introductions in the way that many investors do.
• A rejection does not stop you. Approximately half of the companies in a batch “applied multiple times before being accepted.” YC reads progress since your last application as a strong signal.

YC invests only in corporations of the United States, Canada, the Cayman Islands, or Singapore. A company from a different country must first do a flip: the founders put a new parent company in one of those four places. YC says that a flip “will require a significant effort on your part.” The lesson on setting up the company tells more about the flip.

How many companies YC accepts

YC gives its acceptance rate as a round number, and other websites give many different numbers. Use YC’s own pages first. Then look at the date of each number.

The acceptance rate is the number of companies that YC accepts, divided by the number of applications:

Acceptance rate = Companies accepted ÷ Applications
                = 260 ÷ 27,000
                = 0.96%

Work it out

Trackers counted approximately 199 companies in W26, from approximately 23,000 applications. What was the approximate acceptance rate?

Your answerCheck

The interview

If YC selects an application, the next step is an interview:

• The interview is 10 minutes long, on a video call, and all the founders are on the call.
• Two or three YC partners speak with the founders.
• YC usually makes the decision on the same day, and it gives detailed feedback to each team that it interviews.

For W27, most interviews are by video in November and December 2026. Ten minutes is a short time, so each answer must be short too.

The interview is a conversation, not a fight. Caldwell said that two things give a bad result: an adversarial attitude, and answers that sound “robotic” because a coach trained the founders too much. The question in each partner’s head is simple: “Do I believe I can have a productive working relationship with these founders?” In 2016, Michael Seibel of YC wrote this advice for a pitch: “Make it sound dumber than you think it should.”

Use that advice now. Write each answer in the words that you use when you speak. Then look at the length and the vague words.

Practice · question 1 of 4

Answer like you talk

Type your answer in the words that you use out loud with a YC partner. Short and plain is the goal, not polished.

What does your company do?

Words

0

Aim for 25 or fewer

Sentences

0

One or two

Vague words

0

Words that hide the meaning

Type an answer. The worksheet counts the words and looks for words that sound good but tell the listener nothing.

Next questionShow an example

The money comes first

YC does not wait for the batch to start. The YC deal page says: “The day a company is accepted to YC, we commit to investing our standard deal and begin the process to do so immediately.” No milestones are necessary for the investment, and YC charges the company no fees.

Inside the batch

A batch has a clear structure. It puts each founder in a small group inside a large batch:

• A 3-day kickoff in person, in the first few weeks, to meet the other founders and the group partners
• 3 groups, each in sections of 6 to 10 companies
• YC partners for each group, who give advice in office hours: in groups every two weeks, and one-on-one “as often as founders want”
• A direct Slack channel with your partner, and a weekly meeting during the batch
• Weekly meetups in San Francisco, frequently with a guest speaker from the startup world
• More than $12M in free credits and deals from partner companies

YC founders also have a private network called Bookface. YC writes that B2B and consumer companies “often get their first 40-50 paying customers from the YC community.” For a company with no customers at the start, that is a large advantage.

The work of the batch is growth, measured each week. The lesson on growth rates shows why weekly growth compounds fast. The standard is high. In March 2026, YC president Garry Tan wrote a post about W26. He wrote that W26 had three times more companies at $1M of annualized revenue than W25. Average revenue growth was 14% each week. These numbers come from Lobster Capital, which quoted the post.

Demo Day

At the end of the batch, each company pitches to an invited audience of investors and press. The YC Demo Day page gives “approximately 1,500 investors and media.” The Demo Day FAQ gives approximately 1,000, so the count varies. The F26 Demo Day is on Wednesday, December 2, 2026, in San Francisco.

Demo Day starts the round, but it does not close it. The meetings and the commitments come in the weeks near the event. YC writes that in those weeks it helps founders “decipher the real messages in investors’ sometimes deliberately ambiguous responses.” The lesson after Demo Day shows what YC companies raise.

After the batch

Office hours do not stop at Demo Day. YC writes: “We have office hours year round, and startups from all previous cycles can book time whenever they want.” The Bookface network stays open to the founders too.

What if I am not ready to apply?

YC’s free Startup School is an online course of approximately seven weeks, at one to two hours each week. It includes “Modern Startup Funding” by Carolynn Levy, the inventor of the SAFE, and a service to find a cofounder. But do not wait for a perfect moment. YC says that it is a mistake to wait to apply, and you can apply again next season.

Quiz · question 1 of 6

Test what you learned

How many batches does YC operate each year in 2026?

• A1
• B3
• C2
• D4