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S21 companies that raised the most in the last 12 months

The 30 YC S21 companies whose latest reported round, after their YC batch and in the last 12 months, was the largest.

Updated weekly, last on November 9, 2026. Roster from Y Combinator's public directory.

Showing 30 of 30 companies on this list
#CompanyTeam6 mo12 moOpen rolesTotal raisedLast round
1
Web search rebuilt for LLMs
243+46%+117%28$357MSeries C$250M, May 2026
2
Banking, corporate cards, stablecoin payments, available globally.
98+31%+63%3$160MSeries C$100M, Apr 2026
3
Moving Things Around in Space, Imaging Space Objects When We're Not
211  2$128MSeries B$75M, Apr 2026
4
AI-enabled financial automation and intelligence for CPG Brands
121+89%+163%22$75MSeries B$55M, Sep 2026
5
Online Training for Healthcare Jobs
449+12%+33%36$111MSeries C$55M, Jun 2026
6
Fair, simple and accessible financial services
480+4%+15%2$86.8MCorporate round$53M, May 2026
7
Payments powering people
68−1%+8%5$62MSeries B$40M, Jun 2026
8
Building the human layer of AI
104+4%+33%8$64.2MSeries B$40M, Nov 2025
9
We're building fully automated labs for protein engineering
40+29%+43%YC$50.9MSeries A$40M, Aug 2026
10
We visually monitor space objects for governments and defense
125+12%+21%0$38.4MSeries B$26.4M, Sep 2026
11
Payroll-backed loans and cash advances in Latam
48−2%+2%0$28.6MSeries A$24M, Dec 2025
12
We make cancer care at home possible.
67+8%+24%0$60.6MSeries A$21M, Jan 2026
13
Speech and accent coaching app for non-native English speakers
27+29%+69%2$27.1MSeries A$21M, Dec 2025
14
Unlocking the next generation of mRNA medicines
35+21%+35%0$70.9MSeries A$20M, Oct 2026
15
The AI-Native Turnkey Alternative Investment Platform (TAIP)
29+93%+142%YC$18.9MSeries A$15M, Sep 2026
16
Automated e2e screenshot testing without writing or maintaining tests
28+8%+87%YC$19.1MSeries A$15M, Jul 2026
17
Loan management software for private lenders
30+3%+76%1$13.6MSeries A$13.5M, Feb 2026
18
Discovering drugs that target the DNA regulome
24−8%−8%0$27.8MSeed$11.2M, Sep 2026
19
Developer friendly drop in payouts infrastructure
18+20%+50%YC$14.8MSeries A$8.9M, Feb 2026
20
The Best Data Infrastructure for Biotechs
1  YC$9.7MSeries A$8M, Jun 2026
21
We make software for bookkeepers.
81−2%−9%1$15.1MSeries A$6.5M, Dec 2025
22
Autonomous medical care
40+18%+60%15$7.6MSeed$5.6M, Jan 2026
23
Advanced Contract MFG for fast moving hardware companies
7  0$4.5MPre-seed$4.5M, Dec 2025
24
Plaid for Brazil: we allow developers to access users' financial data
48+33%+71%0$5.2MSeries A$3.5M, Aug 2026
25
Truss is a banking and payments network for blue-collar trades.
14+8%−12%1$8MUndisclosed round$3M, Apr 2026
26
Nuclear-inspired cooling that turns wasted power into more AI compute
16−6% 0$3.5MUndisclosed round$1.3M, Feb 2026
27
One-hour antibiotic sensitivity testing
14+8%+17%0$3.6MSeed$750K, Aug 2026
28
Uber for Healthcare in Latinamerica
71−1%−7%0$43.1MSeries B$750K, Jan 2026
29
Vertical takeoff and landing aircraft for major airlines
51−4%+11%3$42.1MUndisclosed round$173K, Apr 2026
30
Pioneering Breast Cancer Diagnostics for a Healthier Tomorrow
19+6%+6%0$261KSeed$136K, Jun 2026

How this works

1. The roster

Every launched company in YC's public directory, with its batch, status, industry and location. New companies show up the week YC lists them.

2. The numbers

Each company is matched to Crustdata by its website. Crustdata adds team size and its change over 6 and 12 months, open roles from job postings, reported funding, and founders' past employers.

3. The lists

Hiring the most counts distinct roles posted in the last 60 days. Growth needs 10+ people today, shrinking 20+ a year ago, so tiny teams do not top the lists. Rebuilt every week.

Built with Crustdata. Get your own API key and build your own.

The numbers on this page come from three Crustdata API calls. Crustdata tags 5,000+ companies with Y Combinator as an investor; swap the filter for any investor, industry or headcount range and track your own list, with founders' work emails one call away.

  • Company search for team size, growth and funding
  • Job search with a count by company, for who is hiring and for what
  • A watch that re-runs the search weekly and sends only what changed
# 1. every company with Y Combinator as an investor
curl https://api.crustdata.com/company/search \
  -H "authorization: Bearer $CRUSTDATA_API_KEY" \
  -H "x-api-version: 2025-11-01" \
  -d '{
    "filters": { "field": "funding.investors",
                 "type": "in", "value": ["Y Combinator"] },
    "fields": ["basic_info.name",
      "headcount.total", "headcount.growth_percent",
      "funding.total_investment_usd"],
    "limit": 100
  }'

# 2. open listings per company, last 60 days (limit 0 = counts only)
curl https://api.crustdata.com/job/search \
  -H "authorization: Bearer $CRUSTDATA_API_KEY" \
  -H "x-api-version: 2025-11-01" \
  -d '{
  "filters": { "op": "and", "conditions": [
    { "field": "company.basic_info.company_id",
      "type": "in", "value": [...] },
    { "field": "metadata.date_added",
      "type": "=>", "value": "2026-08-24" } ]},
  "limit": 0,
  "aggregations": [{ "type": "group_by",
    "field": "company.basic_info.company_id", "agg": "count" }]
}'

# 3. the same company filter as a weekly watch: POST /watch/company/search

Questions about YC S21 companies

How many YC S21 companies are there?

390 companies were in Y Combinator's Summer 2021 batch (S21); 284 are active.

Which YC S21 companies are hiring?

50 companies posted roles in the last 60 days, led by Stepful (36 roles), Exa (28 roles) and ARQ (24 roles). 85 mark themselves as hiring on YC's directory.

Which YC S21 companies are growing fastest?

By team growth over 6 months (10+ people): Hirebolt (+100%), Aqua (+93%) and Confido (+89%).

Which YC S21 companies raised the most?

Largest latest rounds in the last 12 months, after their YC batch: Exa ($250M), Slash ($100M) and Turion Space ($75M).

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