Y Combinator

What it is

Y Combinator (YC) is a US startup accelerator headquartered in San Francisco, California. Founded in March 2005, it runs four three-month cohorts each year, investing US$500,000 in each accepted company: US$125,000 for a 7% equity stake on a post-money SAFE, plus US$375,000 on an uncapped SAFE with a most-favored-nation clause. Founders relocate to San Francisco for 11 weeks of mentorship, small-group office hours, and Demo Day preparation. The program accepts pre-revenue and pre-product teams from any country, with no sector restriction. The Summer 2025 cohort's 0.6% acceptance rate was the lowest on record, making admission among the most selective events in global technology.

History

Paul Graham, Jessica Livingston, Robert Tappan Morris, and Trevor Blackwell launched YC in Cambridge, Massachusetts in March 2005, inviting eight founding teams to accept a modest equity investment and spend a summer building. Reddit emerged from that first cohort. By 2009 YC had consolidated entirely to Mountain View, California. Sam Altman took over as president in 2014 and held the role through 2019, scaling cohorts from dozens to hundreds of companies per batch. Geoff Ralston succeeded Altman and in 2022 deliberately cut batch size by 40%, from 414 to roughly 250, to restore deal quality. In January 2023, Garry Tan, a YC alumnus and Initialized Capital co-founder, became president and CEO, the third person to lead the organization. YC moved its headquarters from Mountain View to San Francisco in spring 2023.

Current state

As of mid-2026, YC has backed more than 5,600 companies, which together carry a combined valuation exceeding US$600 billion. More than 100 alumni have crossed the US$1 billion valuation mark, among them Airbnb, Coinbase, DoorDash, Dropbox, Instacart, Reddit, Scale AI, Stripe, and Twitch. YC now runs four batches a year, keeping cohort sizes in the 140-200 company range. The Spring 2026 Demo Day, detailed in YCのスプリング2026デモデーに196社が登場、オンチェーンUSDCシード投資も初解禁, fielded 196 companies and introduced YC's first fully on-chain seed disbursement: all accepted founders could elect to receive their US$500,000 investment in USDC stablecoins. Garry Tan's Requests for Startups signal current editorial priorities: AI-native services, counter-drone defense technology, and precision agriculture, areas YC considers structurally underserved as of mid-2026.

Relationships

The YC alumni network operates as a self-reinforcing investment ecosystem. Founders from early batches became angel investors and limited partners who then backed later cohorts and adjacent vehicles, a dynamic visible in the emergence of dedicated YC-focused funds totaling hundreds of millions of dollars by 2025. Stripe and Airbnb alone have produced multiple serial entrepreneurs who now seed new cohorts. Portfolio health is not uniform: YC-backed Parker filed Chapter 7 in May 2026, after raising US$200 million and failing a last-stage US$90 million acquisition, exposing regulatory gaps in the embedded-finance model. YC's Hacker News, launched in 2007, serves as the accelerator's de facto editorial arm, reaching millions of developers and founders globally and functioning as a primary distribution channel for technology discourse.

What to watch

Garry Tan faces two structural pressures heading into late 2026: sustaining deal quality as competition for AI-native founding teams intensifies from well-capitalized rival programs, and defending YC's per-company valuation authority as seed-stage multiples compress from 2021 highs. The S26 on-chain USDC experiment will be a data point on whether stablecoin disbursements reduce friction or introduce compliance complexity for early-stage US companies. Any US regulatory action on AI model deployment or crypto infrastructure disproportionately affects YC's current portfolio composition, given the AI and fintech concentration in recent batches.