Welcome to the second edition of our Batch Testing series, where we track how every YC cohort has performed post-YC. We began with the YC 2020 batch, tracking growth trajectories and key metrics to assess how the startups performed over five years. This time, we’re breaking down YC 2021 outcomes four years later.

Y Combinator funded a record 727 startups in 2021 across its Winter and Summer batches, marking its largest year ever.

By 2021, pandemic uncertainty had given way to a funding frenzy. Instacart hit $39B, Tiger Global wrote checks in 48 hours, and SPACs flooded the market. YC also went all in.

The Winter 2021 batch included 350 startups, and the Summer batch grew to 402. While Demo Days remained virtual, 3,000+ investors still showed up, unlocking record seed funding.

A total of 47 countries were represented across both batches. And for the first time in YC’s history, about ~50% of the startups in the cohort were based outside the US. The top non-US countries included India (33 companies), the UK (18), Canada (18), Mexico (17), Singapore (12), and Brazil (11).

Four years later, we're measuring whether that conviction paid off.

Let’s rewind to 2021.

The Bets

B2B SaaS, Fintech, and Consumer startups have historically driven YC's biggest outcomes (Stripe, Airbnb, Coinbase), and 2021 showed continued concentration here.

B2B Software remained a top category, but its share fell from 45% in 2020 to 37% in 2021.
This suggests YC broadened its intake beyond core SaaS, even while keeping B2B as the backbone of the cohort.

Consumer held steady at 14-15% across both years.
It ranked third in 2020 and 2021, showing consistent interest in consumer products.

Healthcare declined from 15% in 2020 to 10% in 2021.
It was the second most funded sector in 2020, but only came in fourth in 2021, indicating a relative cooling in YC’s healthcare intake year over year.

DevTools emerged as a notable category in 2021 at 8%.
This shows YC’s growing emphasis on developer-first and infra tooling, likely influenced by cloud, AI, and remote-first software trends at the time.

Capital-intensive sectors attracted minimal interest.
Aerospace/Aviation (1%), Climate/Energy/Sustainability (2%), and Industrials (3%) combined for just 6% of the batch, reflecting YC's historical focus on software and digital products.

To get a more detailed view, we can further break down the categories into specific verticals that got the most funding.

What's interesting to note here is the share of AI startups. It represented just 1.5% of the YC 2021 batch. By 2025, AI agents alone made up 46% of YC's Spring batch, and 88% of Summer startups were AI-native. This shows how quickly the sector has exploded in just 4 years!!