Y Combinator · S21
Y Combinator Summer 2021 startups
RemJobs lists 287 startups from Y Combinator's Summer 2021 batch. 134 of the 287 startups are based in the United States, and 56 in San Francisco. Between them they are in 36 countries and 100 cities. 19 are hiring remotely.
Updated
- startups
- 287
- countries
- 36
- cities
- 100
- hiring remotely
- 19
Summer 2021 startups
- KodexYC S21Kodex makes it easy for companies to process, and respond to, subpoenas from governments around the world. Agencies, like the FBI, subpoena user data from customers like Coinbase… Sydney, Australia Remote: Australia, Ireland +2
- LemFiYC S21LemFi makes everyday financial services fair, simple and accessible for people overlooked by traditional banks, starting with those who live and work across borders Soho, United Kingdom Remote: Europe, United Kingdom +2
- AdaptyvYC S21Proteins are the most advanced nanotechnology we know of. At Adaptyv, we’re building a fully automated protein foundry to allow you to synthesize and test any protein you design. Epalinges, Switzerland Remote: Switzerland, United Kingdom +1
- LagoYC S21Scale your AI or tech business with Lago: event-driven usage metering, hybrid pricing, and open-source or cloud deployment. Remote: Europe
- Parallel BioYC S21Parallel Bio is pioneering human-first drug discovery by creating the first map of human biology. Using groundbreaking biological and computational tools that track real clinical… Cambridge, United States Remote: United States
- BarakaYC S21Investing app that lets people in the UAE and GCC buy US stocks, ETFs, options and gold. Dubai, United Arab Emirates
Members only
281 more S21 startups
Unlock the full list, every company on the map, and their founders, emails, LinkedIn and careers pages.
Where they are
68 more in other countries or with no known location
Hiring remotely
19 startups from S21 had at least one open remote role when their job boards were last read, 229 remote roles between them.
Other batches
Questions
How many startups are in Y Combinator's Summer 2021 batch?
RemJobs lists 287 startups from the Summer 2021 batch (S21) as of Oct 2, 2026, including Kodex, LemFi, Adaptyv, Lago and Parallel Bio. The count covers the companies we have found, which may be fewer than the batch itself.
Where are Y Combinator Summer 2021 startups based?
134 of the 287 startups are based in the United States, and 56 in San Francisco. Between them they are in 36 countries and 100 cities. By country: United States (134), India (22), United Kingdom (16), Mexico (13) and Brazil (10).
Which S21 startups are hiring remotely?
19 startups had open remote roles when their job boards were last read, 229 remote roles between them, including Kodex, LemFi, Adaptyv, Lago and Parallel Bio.
Can I contact the founders of S21 startups?
Each company has a free public profile. 22 of them have founder names on file, and members see the founders, their emails where found, LinkedIn and careers pages, and every company on the map.
Companies come from public sources: their own websites, public startup directories and accelerator portfolios, and their public job boards (Greenhouse, Lever, Ashby), which were last read through Oct 2, 2026. A company that is missing or out of date can write to us from the footer.