Y Combinator, LLC (YC) is an American technology
startup accelerator and venture capital firm launched in March 2005 which has been used to launch more than 5,000 companies.
The accelerator program started in
Boston
Boston is the capital and most populous city in the Commonwealth (U.S. state), Commonwealth of Massachusetts in the United States. The city serves as the cultural and Financial centre, financial center of New England, a region of the Northeas ...
and
Mountain View, expanded to
San Francisco
San Francisco, officially the City and County of San Francisco, is a commercial, Financial District, San Francisco, financial, and Culture of San Francisco, cultural center of Northern California. With a population of 827,526 residents as of ...
in 2019, and was entirely online during the
COVID-19 pandemic
The COVID-19 pandemic (also known as the coronavirus pandemic and COVID pandemic), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), began with an disease outbreak, outbreak of COVID-19 in Wuhan, China, in December ...
. Companies started via Y Combinator include
Airbnb,
Coinbase,
Cruise,
DoorDash,
Dropbox,
Instacart,
Reddit
Reddit ( ) is an American Proprietary software, proprietary social news news aggregator, aggregation and Internet forum, forum Social media, social media platform. Registered users (commonly referred to as "redditors") submit content to the ...
,
Stripe,
Scale AI,
Deel,
Helion Energy, and
Twitch.
History
Founded in 2005 by
Paul Graham,
Jessica Livingston,
Robert Tappan Morris, and
Trevor Blackwell, Y Combinator (YC) initiated operations with concurrent programs in
Cambridge, Massachusetts
Cambridge ( ) is a city in Middlesex County, Massachusetts, United States. It is a suburb in the Greater Boston metropolitan area, located directly across the Charles River from Boston. The city's population as of the 2020 United States census, ...
, and
Mountain View, California
Mountain View is a city in Santa Clara County, California, United States, part of the San Francisco Bay Area. Named for its views of the Santa Cruz Mountains, the population was 82,376 at the 2020 United States census, 2020 census.
Mountain V ...
. However, operational complexities arising from managing two programs prompted a consolidation in January 2009, resulting in the closing of the Cambridge program and the centralization of activities in Silicon Valley.
Although often overlooked in early accounts, Jessica Livingston played a pivotal role in shaping Y Combinator's culture and success. As co-founder, she was instrumental in the organization's day-to-day operations and, crucially, in selecting founders.
In 2009, Y Combinator secured a $2 million investment led by
Sequoia Capital, enabling increased annual funding for around 60 companies. Sequoia further supported YC in 2010 through an $8.25 million funding round, bolstering the organization's capability to accommodate a growing number of startups. Concurrently, Kirsty Nathoo joined the team, initially as an accountant, and subsequently as the Chief Financial Officer (CFO) in 2012. In 2011,
Yuri Milner and
SV Angel offered every Y Combinator company a $150,000 convertible note investment. The amount put into each company was changed to $80,000 when Start Fund was renewed.

Advisory roles were assumed by
Harj Taggar and
Alexis Ohanian
Alexis Kerry Ohanian (; born April 24, 1983) is an American internet entrepreneur and investor. He is best known as the co-founder and former executive chairman of the social media site Reddit along with Steve Huffman and Aaron Swartz. He also ...
in 2010, and
Paul Buchheit and Taggar were named partners in November.
Michael Seibel joined Y Combinator as a part-time partner in January 2013 before becoming a full-time partner in 2014.
In September 2013, Y Combinator began funding nonprofit organizations that were accepted into the program after testing the concept with
Watsi.
Sam Altman took part in Y Combinator's inaugural cohort in 2005 as a founder. In 2014, Paul Graham appointed him as President.
Altman introduced a revised equity offering of $150,000 for a 7% stake.
Global outreach became evident in 2016 as YC partners embarked on visits to 11 countries (
Nigeria
Nigeria, officially the Federal Republic of Nigeria, is a country in West Africa. It is situated between the Sahel to the north and the Gulf of Guinea in the Atlantic Ocean to the south. It covers an area of . With Demographics of Nigeria, ...
,
Denmark
Denmark is a Nordic countries, Nordic country in Northern Europe. It is the metropole and most populous constituent of the Kingdom of Denmark,, . also known as the Danish Realm, a constitutionally unitary state that includes the Autonomous a ...
,
Portugal
Portugal, officially the Portuguese Republic, is a country on the Iberian Peninsula in Southwestern Europe. Featuring Cabo da Roca, the westernmost point in continental Europe, Portugal borders Spain to its north and east, with which it share ...
,
Sweden
Sweden, formally the Kingdom of Sweden, is a Nordic countries, Nordic country located on the Scandinavian Peninsula in Northern Europe. It borders Norway to the west and north, and Finland to the east. At , Sweden is the largest Nordic count ...
,
Germany
Germany, officially the Federal Republic of Germany, is a country in Central Europe. It lies between the Baltic Sea and the North Sea to the north and the Alps to the south. Its sixteen States of Germany, constituent states have a total popu ...
,
Russia
Russia, or the Russian Federation, is a country spanning Eastern Europe and North Asia. It is the list of countries and dependencies by area, largest country in the world, and extends across Time in Russia, eleven time zones, sharing Borders ...
,
Argentina
Argentina, officially the Argentine Republic, is a country in the southern half of South America. It covers an area of , making it the List of South American countries by area, second-largest country in South America after Brazil, the fourt ...
,
Chile
Chile, officially the Republic of Chile, is a country in western South America. It is the southernmost country in the world and the closest to Antarctica, stretching along a narrow strip of land between the Andes, Andes Mountains and the Paci ...
,
Mexico
Mexico, officially the United Mexican States, is a country in North America. It is the northernmost country in Latin America, and borders the United States to the north, and Guatemala and Belize to the southeast; while having maritime boundar ...
,
Israel
Israel, officially the State of Israel, is a country in West Asia. It Borders of Israel, shares borders with Lebanon to the north, Syria to the north-east, Jordan to the east, Egypt to the south-west, and the Mediterranean Sea to the west. Isr ...
, and
India
India, officially the Republic of India, is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area; the List of countries by population (United Nations), most populous country since ...
) to engage with founders and learn about international startup communities.
That summer, Altman returned to Y Combinator as a founder and worked on
OpenAI. Leadership responsibilities were delegated to
Ali Rowghani and Michael Seibel for YC Continuity and YC Core programs, respectively. Startup School, introduced in 2017, provided startups with online courses and personalized coaching. More than 1500 startups graduated from the program in its first year.
In 2018, Y Combinator announced a new batch of startup schools. After a
software
Software consists of computer programs that instruct the Execution (computing), execution of a computer. Software also includes design documents and specifications.
The history of software is closely tied to the development of digital comput ...
glitch, all 15,000 startups that applied to the program were accepted, only to learn a few hours later that they had been rejected. In response to the ensuing outcry, Y Combinator accepted all 15,000 companies involved in the incident. The same year,
Qi Lu, a former CEO of
Bing and
Baidu, briefly assumed the role of CEO for YC China. In November, YC announced Lu's departure and their decision to not pursue a program in China. YC China later morphed into
MiraclePlus, an accelerator similar to YC, with Lu once again at the helm.
Geoff Ralston succeeded Altman as Y Combinator's president in 2019.
Adapting to the
COVID-19 pandemic
The COVID-19 pandemic (also known as the coronavirus pandemic and COVID pandemic), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), began with an disease outbreak, outbreak of COVID-19 in Wuhan, China, in December ...
, Y Combinator conducted its summer 2020 batch remotely. In January 2022, a revised standard deal of $500,000 was introduced, comprising $125,000 for a 7% equity stake and an additional $375,000 via an uncapped safe mechanism incorporating a
Most Favored Nation (MFN) clause. The summer of 2022 saw a deliberate reduction in the startup intake by 40%, from 414 companies to 250.
In January 2023,
Garry Tan assumed the positions of president and CEO, succeeding Geoff Ralston. Tan's leadership marked the discontinuation of the YC Continuity growth fund.
YC moved its headquarters from
Mountain View to
San Francisco
San Francisco, officially the City and County of San Francisco, is a commercial, Financial District, San Francisco, financial, and Culture of San Francisco, cultural center of Northern California. With a population of 827,526 residents as of ...
in the spring of 2023. It had been considering such a move since 2019.
In March 2024, Seibel stepped down as managing director.
Programs
Y Combinator interviews and selects four batches of companies per year. The companies receive a total of $500,000 in
seed money as well as advice and connections. The $500,000 in funding is made up of $125,000 on a post-money
SAFE in return for 7%
equity and $375,000 on an uncapped SAFE with a "most favored nation" ("MFN") provision (i.e.: "we get the same best terms you give anyone else in the next round"). Non-profits receive a $100,000 donation. The program includes "office hours", where startup founders meet individually and participate in group meetings. Founders also participate in weekly meetups where guests from the
Silicon Valley
Silicon Valley is a region in Northern California that is a global center for high technology and innovation. Located in the southern part of the San Francisco Bay Area, it corresponds roughly to the geographical area of the Santa Clara Valley ...
ecosystem (successful entrepreneurs, venture capitalists, etc.) speak to the founders.
Y Combinator's program is designed to teach founders how to market their product, refine their teams and business models, achieve
product/market fit, and scale the startup into a
high growth business, etc. The program ends with "Demo Day", where startups present their business and technology prototypes to potential investors.
Y Combinator operates additional programs and a fund designed to support and invest in startups which have already graduated from the main accelerator program. The Series A Program, YC Post-A Program, and YC Growth Program are operated by the same team and focus on helping fast-growing YC startups, and startups raising their Series B funding of $20 million to $100 million.
Y Combinator has introduced additional programs since 2015, including:
* In July 2015, Y Combinator introduced the YC Fellowship Program, aimed at companies at an earlier stage than the main program.
The first batch of YC Fellowship included 32 companies that received an equity-free grant instead of an investment.
In January 2016, YC changed the program, with participating companies receiving $20k investment for a 1.5 percent equity stake. The equity stake is structured as a
convertible security that converts into shares only if a company has an
initial public offering
An initial public offering (IPO) or stock launch is a public offering in which shares of a company are sold to institutional investors and usually also to retail (individual) investors. An IPO is typically underwritten by one or more investm ...
(IPO), or a funding event or acquisition that values the company at $100 million or more. The fellowship was discontinued in 2017.
* In October 2015, Y Combinator introduced the now-defunct YC Continuity Fund. The fund allowed Y Combinator to make
pro rata
''Pro rata'' is an adverb or adjective meaning in equal portions or in proportion. The term is used in many legal and economic contexts. The hyphenated spelling ''pro-rata'' for the adjective form is common, as recommended for adjectives by some ...
investments in their alumni companies. The program was shut down, and staff were laid off in March 2023.
*During 2017–2019, YC launched Startup School, the Series A program, the YC Growth program, Work at a Startup, and YC China.
As of 2025, Y Combinator had invested in over 5,000 companies,
most of which are for-profit, holding a combined valuation of $600 billion. Non-profit organizations can also participate in the main YC program. Few non-profits have been accepted in the last years, among them
Watsi,
Women Who Code,
New Story,
SIRUM,
Zidisha,
80,000 Hours, and
Our World in Data.
Research
In October 2015, YC introduced YC Research to fund long-term fundamental research. Altman donated $10m. Researchers were paid as full-time employees and can receive equity in Y Combinator.
OpenAI was the first project undertaken by YC Research, and in January 2016, a second study on
basic income was also announced. Another project was research on new cities.
The Human Advancement Research Community (HARC) project was set up in 2016 with the "mission to ensure human wisdom exceeds human power". The project was inspired by a conversation between Altman and
Alan Kay. Its projects included modelling, visualizing and teaching software, as well as programming languages. Members included Alan Kay,
Dan Ingalls,
Bret Victor,
Vi Hart, and
Patrick Scaglia. HARC was shut down in 2017.
Australian quantum physicist
Michael Nielsen was a research fellow at YC Research from 2016 to 2019.
YC Research disaffiliated with Y Combinator and was renamed to Open Research in 2020.
See also
*
List of Y Combinator startups
*
Hacker News
*
Techstars
*
500 Startups
*
HighTechXL
*
Entrepreneurs Roundtable Accelerator
References
External links
*
Wonderful Performance formerly Y Combinator China
{{Authority control
Business incubators of the United States
Startup accelerators
Venture capital firms of the United States
Financial services companies based in California
Companies based in San Francisco
Financial services companies established in 2005
2005 establishments in California
Business incubators