Read Paul Graham’s initial post announcing YC’s first batch

Y Combinator was founded in 2005 to bridge gaps between founders and investors

In one of Paul Graham’s essays on his website, he took the time to explain how and why he and his cofounders (including his girlfriend at the time, and now wife, Jessica Livingston), came up with the idea of and eventually created Y Combinator.

YC was partly inspired by an investor named Julian Weber

Y Combinator Cofounder Paul Graham’s former professor’s husband Julian Weber provided $10K in seed funding to Graham’s previous startup, Viaweb in its early days. In exchange, Weber received 10% of the company. Weber’s involvement inspired Graham to start a program where investors were more involved with the companies they contributed seed funding to.

Y Combinator cofounder Paul Graham keeps a public archive of his insightful essays

In addition to cofounding Y Combinator and other companies before it, Paul Graham is a prolific writer and artist. He chronicled many of his thoughts while building Y Combinator in a series of dozens of candid essays, all of which you can read in an online archive.

Y Combinator, the startup accelerator, gets its name from the 'Y combinator' computer science concept.

For Reddit's founders, the company's early days included choosing a dinner with Y Combinator's Paul Graham over a spring break trip, a $10M Condé Nast acquisition, and other pivotal moments.

Visualize where the first batch of founders from the famous startup accelerator Y Combinator are now.

Y Combinator cofounder, Jessica Livingston, once interviewed her husband and cofounder, Paul Graham

Two of Y Combinator's cofounders, Jessica Livingston and Paul Graham, were in a romantic relationship before they started the accelerator. They later married, and much later, Livingston started a podcast. In an episode of her podcast, Livingston and her cohost interview Graham about the beginning of YC and more.

Y Combinator changed the way startups around the world are built

Many of the philosophies that the leaders of Y Combinator have infused into the program’s portfolio companies have become the playbook for building the next big thing, such as its focus on founder personality and more.

Stanford’s ‘How to Start a Startup’ series

Stanford’s archive of lectures about creating a startup includes advice from Y Combinator notables such as former YC president and OpenAI CEO Sam Altman and YC Cofounder Paul Graham.

Listen to a podcast episode where Y Combinator CEO Gary Tan explains why YC tends to outperform many other Silicon Valley startup accelerators.

CEO Gary Tan explains Y Combinators guiding philosophy

Hear YC President and CEO Garry Tan talk about why he values earnesty and excellent communication skills in YC founders, his thoughts on AI, and more in this unexpectedly deep and in-depth interview.

The Y Combinator startup directory includes every company YC has funded

The startup accelerator has funded more than 5,000 companies over the years. This YC-specific search engine lets you look up any company to find out if it's a YC alum.

Explore the schedule of a three-month YC batch

During the three months that founders accepted into Y Combinator spend on YC’s California campus, they receive mentorship from YC partners, networking opportunities, and, overall, a ton of time to build and scale their companies.

Yahoo acquired Paul Graham's former startup Viaweb in 1998

Viaweb was the web app tech startup that Paul Graham, Robert Morris, and Trevor Blackwell cofounded before they started Y Combinator. The company sold for $49M and Viaweb was rebranded as the Yahoo Store.

Dive deep into the numbers that shape each YC deal

Y Combinator invests $500K into each company in any given batch. $125K of that investment converts into a fixed 7% in ownership of the startup, and the other $375K is invested on something called an uncapped MFN safe. YC explains what that means and more terms of the deal in a detailed article on their website

87% of the startups in Y Combinator’s Fall 2025 batch were AI companies

Y Combinator also recently increased its number of cohorts or “batches” per year from two to four. Its leaders cited artificial intelligence’s rise as a reason for the increase.

'Founder mode' is the idea that startup founders should take a hands-on approach to running their businesses

In 2024, Y Combinator cofounder Paul Graham popularized the idea of "founder mode" when he wrote a viral manifesto in response to a talk that Airbnb CEO Brian Chesky gave about leadership styles. Graham positioned the concept of founder mode as the opposite of manager mode—when founders hire executives and middle managers to run their companies and make decisions that Graham says are better left to founders.

'Founder mode' is the idea that founders should take a hands-on approach to running their businesses

In 2024, Y Combinator Cofounder Paul Graham wrote a viral manifesto of sorts about a strategy he calls "founder mode." It's the opposite of what Graham calls "manager mode," which allows founders to hire executives who he says ultimately run the company into the ground.

Watch the DoorDash team's YC application video

In 2013, the cofounders of DoorDash created a simple, homemade video application to Y Combinator. They didn't know it at the time, but they'd be accepted—and their company would go on to be publicly traded on the NASDAQ.

Y Combinator has a roughly 1% acceptance rate

That’s lower than the most elite universities and colleges in the world—but insiders have some tips about how applicants can have the best shot of being accepted to the selective startup accelerator.

‘Demo days’ are when founders at Y Combinator pitch their startup ideas

Investors sit in the audience, waiting to hear what this season’s batch of YC founders have cooked up. YC argues that going through the process of a demo day can help founders get a better understanding of their startup themselves.

Startup accelerators that include more training activities, such as pitch competitions, tend to have better long-term success rates

That's according to a new study from Wharton. Y-Combinator, perhaps the most famous startup accelerator, currently has 16 alumni companies trading on the public market. But not every entrepreneur who joins a startup accelerator makes it big.

Startup accelerators offer mentorship and seed funding in exchange for equity

Those programs, such as Y Combinator and Techstars, not only offer expert advice to founders, but also seed funding in exchange for equity. The goal is to help young startups learn from successful companies, making it more likely they attract venture capital.

7 angel investors funded Google in its early days

Entrepreneur Shaan Puri shares how seven strangers acted as Google’s earliest angel investors. The first gave Google $100K without even putting his equity agreement in writing. The investors on “Shark Tank” use their personal funds to support startups, but they’re often more predatory about terms than typical angels.

ChatGPT was conceived over dinner at a Silicon Valley hotel.

Many startup founders pull out-of-the-box stunts to get their businesses off the ground.

How venture capital firms came to be

The venture capital firm that kickstarted an industry.

YouTube began as a quirky site invented by former PayPal employees

In February 2005, YouTube was launched by Steve Chen, Chad Hurley, and Jawed Karim. Their idea was to build a platform to support the convenient sharing of videos online, a relatively novel idea in the days of cable TV and early social media.

Mark Zuckerberg credits some of Facebook's success to constant evolution

Before becoming the head of OpenAI, Sam Altman was the president of Y Combinator—a startup accelerator company that supported companies like Airbnb, DoorDash, and Coinbase. In 2016, Altman interviewed Zuckerberg about creating Facebook and its growth over time. Zuckerberg said that, unlike other companies (think: CourseMatch), Facebook kept growing and adding new features, which prevented the app from becoming obsolete.

Sam Altman gave his first-ever startup pitch after dropping out of Stanford

He dropped out of Stanford to start Loopt, which sold in 2012 for $43.4M. You can watch his first-ever startup pitch in a video.

YouTube was acquired by Google for $1.65B in stock during its second year

In 2006, Google acquired YouTube for $1.65B, only two years after its launch. Sequoia Capital, one of Silicon Valley's best-known venture firms, was an early investor in the streaming video platform, seeing it as the next step in the evolution of user-generated content that flourished online during the mid-2000s.

Apple's first backer recruited his own CEO to help manage the company

Wanting Steve Jobs and Steve Wozniak to focus on developing Apple computers, Mike Markkula brought in his colleague from Fairchild Semiconductor, Michael Scott. As employee number five, Scott helped professionalize the fledgling computer company and getting manufacturing off the ground. (Some users may experience a paywall.)

The term 'startup'—which is typically used to describe private companies in their early stages of operation that focus on innovating new products or services to meet a market gap—can be traced back to a 1976 Forbes article.

Uber's first investors included StumbleUpon founder Garrett Camp

In 2010 when Uber went out to raise money, prominent investors including Mark Cuban and Gary Vaynerchuk passed. Vaynerchuk actually said no twice.

The first-ever tweet on X was sent on March 21, 2006, at 9:50 pm

The short, declarative message launched what would eventually become one of the world's most influential social media platforms. As of 2020, about 10% of X users are responsible for 92% of all posts.

Prediction market Polymarket's CEO dropped out of New York University

Polymarket CEO Shayne Coplan started building Polymarket when he was 21. Polymarket has been backed by billionaire investors such as Peter Thiel and Vitalik Buterin.

The early success of Facebook made Mark Zuckerberg a college campus celebrity

Within 24 hours of launching in 2004, more than 1,200 Harvard students signed up to the platform, which quickly expanded to other Ivy League and Boston-area schools within months. By year's end, Zuckerberg left Harvard to run the company in California.

The dot-com bubble burst in the early 2000s

If you’ve heard of companies like Google and Yahoo, you’re already partially familiar with the dot-com bubble: a period from roughly 1995 to 2001, when internet companies were the hottest thing in venture capital. The “bubble” part of the term refers to the industry’s eventual implosion.

From 19th-century whalers to startup accelerators, venture capital has a pretty exciting history

While the aforementioned whaling industry has a lot of similarities to today’s venture fund models, the first modern venture capital firm wasn’t founded until 1946.

Peter Thiel and Elon Musk formed PayPal after merging two dot-com companies

Elon Musk cofounded "X.com," an online banking service, in 1999 with the idea that the web would become a financial repository as internet access expanded and became ingrained in daily life. Peter Thiel cofounded "Confinity" as a digital security service that morphed into a payments system. In 2000, the two merged to form PayPal, and in 2002, they sold PayPal to eBay for $1.5B.

Three AI startup founders broke the record for the youngest self-made billionaire previously set by Mark Zuckerberg

Mark Zuckerberg became the youngest self-made billionaire in 2006 at 23 years old when Facebook held its initial public offering. In January of 2026, three AI startup founders—Brendan Foody, Adarsh Hiremath, and Surya Midha—broke Zuckerberg's record and became billionaires at 22 years old.

7 prominent investors rejected Airbnb in its early days

Airbnb is arguably known as one of the most successful startup stories of all time. But back in 2008, many prominent investors rejected their pitch when they went out to raise money—and Airbnb's founder still has the rejection emails to prove it.

See Don Valentine's original 1977 memo for Sequoia's investment into Apple Computer

In honor of Apple's 50-year anniversary, Sequoia Capital recently posted a tweet on X (the social media platform formerly known as Twitter) with a photo of the original 1977 memo for Sequoia's investment in Apple.

Andreessen Horowitz is among the most well-known venture capital firms

Also known as a16z, the firm has invested in companies such as Airbnb, Facebook, and Lyft since its founding in 2009. A podcast episode offers a deep dive into how the firm got started and became the industry disruptor it is today.

The history of Reddit, the front page of the internet

The hyperactive online forum and social media platform has transformed since 2006 from a simple link-sharing site to a behemoth in digital media. Topping off its ascendancy, Reddit went public on the New York Stock Exchange in 2024, solidifying its future amid a shifting technological climate. Dive into Reddit's nearly two decades of growth with this detailed timeline.

Startups follow a 'minimum viable product' strategy to determine demand

Michael Seibel, group partner for startup incubator Y Combinator, explains how to build a minimum viable product (also known as an MVP) for any startup idea. Using real companies that experienced the Y Combinator program as examples, he walks through how to determine an MVP feature set, how to present an MVP to potential investors, and more.

Amazon sends its first-ever letter to shareholders every year

The first letter to Amazon’s shareholders, written by founder and then-CEO Jeff Bezos in 1997, is a key part of the Amazon story—laying out the company’s long-term approach to the business and several of its core operating values. Bezos emphasizes, for example, Amazon’s plan to start with a bookstore but to evolve into a much larger ecosystem.

Watch a rare early interview with Palantir CEO Alex Karp

Prior to Palantir's public listing in 2020, CEO Alex Karp did not give many interviews. In a rare interview from 2009, Karp discussed the dominance of American technology, his academic background, and the founding idea of Silicon Valley entrepreneurs as key players in aiding the fight against terrorism.

Apple’s third cofounder was its angel investor

Steve Jobs and Steve Wozniak are well-known for cofounding Apple, but the company had a third founder who acted as an angel investor: Mike Markkula, who invested $250K in 1977.

Many original dot-com company founders were bought out early on

The people who bought the original domains for dot-com companies and had the ideas to start businesses were often bought out by investors before becoming well-known companies. Both Pets.com and Broadcast.com were acquired early on.