BATCH INDEX · 2005–2026
The complete YC batch list, S05 to S26.
Every Y Combinator batch since the first eight companies in Summer 2005 — season, dates, how many companies got in, and who came out of it. Jump straight to a batch hub below.
Jump to a batch hub
Every YC batch, 2005–2026
Sizes marked with ~ are estimates from public batch directories; YC only confirms exact counts for some batches. Alumni listed are the best-known company from that batch, not the full list.
| Batch | Term | Companies | Notable / notes |
|---|---|---|---|
| S05 | Summer 2005 | 8 | Reddit, Loopt |
| W06 | Winter 2006 | ~11 | — |
| S06 | Summer 2006 | ~11 | — |
| W07 | Winter 2007 | ~19 | Justin.tv (Twitch), Disqus |
| S07 | Summer 2007 | ~19 | Dropbox, Weebly |
| W08 | Winter 2008 | ~22 | Zenter, Snaptalent |
| S08 | Summer 2008 | ~22 | Heroku |
| W09 | Winter 2009 | ~16 | Airbnb |
| S09 | Summer 2009 | ~26 | Stripe, Cloudkick |
| W10 | Winter 2010 | ~26 | — |
| S10 | Summer 2010 | ~36 | — |
| W11 | Winter 2011 | ~43 | — |
| S11 | Summer 2011 | ~63 | Codecademy, Parse |
| W12 | Winter 2012 | ~65 | Gusto (ZenPayroll) |
| S12 | Summer 2012 | ~84 | Coinbase, Instacart |
| W13 | Winter 2013 | ~47 | Zenefits |
| S13 | Summer 2013 | ~53 | DoorDash |
| W14 | Winter 2014 | ~65 | Cruise, Flexport |
| S14 | Summer 2014 | ~80 | Ginkgo Bioworks |
| W15 | Winter 2015 | ~114 | GitLab, Razorpay |
| S15 | Summer 2015 | ~105 | Vanta (later), Standard Cognition |
| W16 | Winter 2016 | ~125 | Rappi |
| S16 | Summer 2016 | ~89 | Zapier alumni network era |
| W17 | Winter 2017 | ~105 | Brex |
| S17 | Summer 2017 | ~124 | Rippling |
| W18 | Winter 2018 | ~141 | Podium era, Front-office SaaS |
| S18 | Summer 2018 | ~132 | — |
| W19 | Winter 2019 | ~200 | Deel |
| S19 | Summer 2019 | ~197 | — |
| W20 | Winter 2020 | ~229 | — |
| S20 | Summer 2020 | ~197 | First fully remote batch |
| W21 | Winter 2021 | ~319 | Zepto |
| S21 | Summer 2021 | ~377 | Largest batch to date |
| W22 | Winter 2022 | ~414 | Peak batch size |
| S22 | Summer 2022 | ~240 | Deliberate downsizing begins |
| W23 | Winter 2023 | ~282 | First big AI wave |
| S23 | Summer 2023 | ~229 | LLM tooling boom |
| W24 | Winter 2024 | ~260 | AI agents dominate |
| S24 | Summer 2024 | ~255 | Vertical AI |
| F24 | Fall 2024 | ~95 | First-ever Fall batch |
| W25 | Winter 2025 | ~160 | In-person SF requirement |
| X25 | Spring 2025 | ~140 | Spring track added |
| S25 | Summer 2025 | ~160 | AI-native majority |
| F25 | Fall 2025 | ~150 | Four-batch year established |
| W26 | Winter 2026 | ~150–250 | Running now |
| S26 | Summer 2026 | TBD | Applications open |
How YC batch names work
A YC batch code is one letter plus two digits. W is Winter, S is Summer, F is Fall and X is Spring — X is used because S was already taken. So W25 is the Winter 2025 batch and F25 is Fall 2025.
YC ran two batches a year from 2005 until Fall 2024, when it added a third, then moved to a four-batch calendar. That means four Demo Days a year and four application deadlines — see the 2026 deadlines for the current windows.
Batch size peaked at roughly 400 companies in W22, then YC deliberately shrank batches back toward 150–250 so partners could spend more time per company. The acceptance rate has stayed near 1% because applications grew as batches shrank.
Whatever batch you land in, the terms are identical: $125K for 7% plus $375K on an uncapped MFN SAFE.
YC batch FAQ
How many YC batches have there been?
Y Combinator has run more than 45 batches since Summer 2005. It started with two batches a year (Winter and Summer) and moved to four a year — Winter, Spring, Summer and Fall — starting with the Fall 2024 batch.
What do YC batch names like W25 and S25 mean?
The letter is the season and the number is the year. W25 is Winter 2025, S25 is Summer 2025, F24 is Fall 2024, and X25 is the Spring 2025 batch. YC uses X rather than S for Spring to avoid clashing with Summer.
Which YC batch was the biggest?
Winter 2022 was the largest at roughly 400+ companies. YC deliberately cut batch sizes afterwards, and recent batches have run closer to 150–250 companies each.
Which YC batch produced the most valuable companies?
Winter 2009 (Airbnb) and Summer 2009 (Stripe) are the two highest-value batches by far. Summer 2012 produced both Coinbase and Instacart, and Summer 2005 — the very first batch — produced Reddit.
How many batches does YC run per year now?
Four: Winter (January–March), Spring (April–June), Summer (June–September) and Fall (October–December). Each batch ends with its own Demo Day.
Free tools for this
- YC Deadline Countdown
Live countdown to the next YC batch deadline.
- YC Application Answer Generator
Draft each application answer with the good-answer formula.
- YC Interview Simulator
Timed practice on the 10 questions partners actually ask.
See all free YC tools.
Free YC databases
Everything behind this page is in our open databases
Batch lists, rejection case studies, RFS playbooks and launch guides — all free to read, no signup.
Playbook
RFS Playbook 2026 →
All 15 YC Request for Startups ideas, each turned into a customer, wedge and 90-day plan.
Database
YC Rejection Database →
Airbnb, Stripe, Reddit — founders who got rejected first, with every source linked.
Playbook
Product Hunt Launch Playbook →
Hour-by-hour launch day playbook calibrated to the 2026 Product Hunt algorithm.
Browse all free YC databases → · or start on the YCInsight homepage
Keep reading
Batch
YC Winter 2025 Batch →
W25 companies, themes, and standout AI startups.
Batch
YC Summer 2025 Batch →
S25 companies and what changed from W25.
Batch
YC W26 Batch →
Winter 2026 dates, Demo Day, batch size and the $500K deal.
Batch
YC S26 Batch →
Summer 2026 dates, deadline, and your application timeline.
Batch
YC 2026 Batches →
W26, S26, F26 timeline, deadlines, and what to expect.
Database
List of YC Companies →
Searchable database of YC alumni by batch — Airbnb to Cursor.
Data
YC Acceptance Rate →
1–2% overall, ~20% after interview — the real numbers batch by batch.
Stories
Founder Stories →
70+ deeply-reported founder journeys from YC alumni.
New here? Start on the YCInsight homepage — every YC database, founder story and Q&A in one place. Or jump straight to the free YC databases.