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Fastest growing W21 companies

The 89 YC W21 companies whose team grew the most in the last 6 months (active companies with 10+ people).

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

Showing 89 of 89 companies on this list
#CompanyTeam6 mo12 moOpen rolesTotal raisedLast round
1
The open source AI coding agent
21+200% 0
2
Meet qualified leads in person by automating conference production
30+58%+50%YCSeedMar 2021
3
Voice AI for developers.
150+50%+114%4$70.6MSeries B$50M, May 2026
4
AI Agents for Oncology EHRs
98+48%+72%3$37.1MSeries B$22M, May 2026
5
Recover from any outage in 10 minutes or less.
51+46%+65%0$26.2MSeries A$15.9M, Jun 2026
6
The one-stop-shop for auto-parts in Mexico.
53+43%+66%0$5.5MSeed$3M, Jan 2023
7
AI recruiter that runs outbound sourcing campaigns to find top talent
266+38%+62%YC$2.2MSeed$2.2M, Aug 2023
8
Get up and running with large language models.
77+38%+64%0$80.1MSeries B$65M, Jul 2026
9
AI tax workflow platform for accounting firms
59+37%+16%YC$4.3MSeries A$4.3M, Aug 2025
10
The Most-Loved IT Documentation Platform
42+35%+50%3$5.1MSeries A$5M, May 2023
11
all-in-one operating system (OS) for telcos
121+34%+51%8$66.3MSeries B$40M, Mar 2026
12
The highest-accuracy global weather data from low-cost flat satellites
12+33%+50%0SeedApr 2024
13
The AI-native FP&A platform that helps Finance teams drive business…
196+32%+54%4
14
The data layer for physical AI
231+31%+75%3$110MSeries C$60M, Feb 2026
15
Ramp for Indian Businesses - UPI Wallets for Employee Expenses
43+30%+87%0
16
33+22%+27%YC$5.3MSeed$5.2M, Jul 2023
17
Admin automation for healthcare
145+22%+54%1$33.1MSeries B$30M, Feb 2025
18
SpruceID lets users control their data across the web.
36+20%+20%4$41.6MSeries A$34M, Apr 2022
19
Interactive product demos
73+20%+30%0$5.4MSeed$4.2M, Mar 2022
20
The OS for Embedded Telecom
318+20%+51%YC$97MSeries B$73M, Dec 2024
21
Government-funded online addiction treatment
45+18%+41%7SeedMar 2021
22
Pay, Get Paid and Extend Cash Flow using your Credit Card as…
13+18%+8%0$125KYC investment$125K, Jan 2023
23
Internet for the urban developing world.
382+18%+41%0$75.6MSeries B$40M, Mar 2026
24
Protecting the grid today, preparing the grid for tomorrow
221+18%+51%1$97.2MSeries B$55M, Nov 2025
25
Seamless mobility to, through, and from space. It starts with 100%…
451+17%+33%4$2.4BSeries E$1B, Sep 2026
26
Software for pharmacies to move beyond dispensing
77+17%+18%YC$3.5MDebt$2.7M, Aug 2025
27
Software orchestrated mass production of plastics
64+16%+49%2$45.3MSeries A$25M, Jun 2025
28
A digital wallet for the Middle East & North Africa
324+15%+45%5$30.5MSeries A$22M, May 2026
29
Full-stack VLEO satellite missions
78+13%+20%6$103MSeries A$35M, Jan 2024
30
AI-Powered HRIS for high performing teams
61+13%+17%2$20MSeries A$15M, Oct 2022
31
Modular carbon capture
79+13%+23%0$5.5MSeries A$5.5M, Feb 2024
32
Modernizing commercial insurance
107+11%+43%17$61.6MSeries B$42M, Mar 2026
33
Operating System for Hotels and Vacation Rentals
89+11%+10%YC$2.4MSeed$2M, Jun 2021
34
Account-to-Account payments in Mexico and Chile.
120+11%+36%0$10.7MSeries A$7M, Apr 2024
35
Automated investing for the next generation 💸
40+11%+29%1$44.3MDebt$22.5M, Feb 2026
36
All-electric seagliders for fast, affordable regional transportation
288+11%+15%30$327MDebt$120M, Aug 2026
37
The unbiased AI and data layer for skin health.
31+11%+7%0$965KPre-seed$840K, Dec 2021
38
The AI operating system for restaurants
214+10%+13%1$2.3MSeed$2.3M, Apr 2021
39
API for developers and AIs to access health data
22+10%+5%YC$2.8MSeed$2.8M, Jun 2021
40
AI workers for the logistics industry.
11+10%−21%YC$6.5MSeed$6.5M, Sep 2023
41
Helping B2B co's sync data to their customers
11+10%+10%YC$5.2MSeed$5.2M, Sep 2023
42
Code review for DevOps tasks
23+10%+44%0SeedOct 2025
43
Shopify for Beauty and Wellness businesses in Latam
186+9%+23%1$42.8MSeries B$35M, Aug 2025
44
The digital bank for small businesses in the Philippines.
35+9%+9%0$1.6MSeed$1.6M, Jul 2021
45
Analyzing EHR and messaging data to predict disease before it occurs.
12+9% YC$125KYC investment$125K, Jan 2023
46
We help people resolve debt.
133+9%+45%YCSeries AMay 2026
47
Makes it easy for tech platforms to embed insurance into products
64+8%+8%2$28.8MSeries A$25M, Feb 2022
48
Juicy marbles makes thick juicy and marbled plant based steaks.
39+8%+5%0$4.5MSeed$4.5M, Nov 2021
49
A better way to write.
13+8% 0Pre-seedNov 2022
50
The super app for pets
13+8%+44%0$1.3MPre-seed$1.3M, Nov 2021
51
Source better parts by partnering directly with vetted manufacturers
122+8%+30%1$16.1MSeries A$12.1M, Nov 2025
52
Better Business on WhatsApp
42+8%+20%0$1.4MSeed$1.4M, Jul 2022
53
The modern, open source, self-hosted AI customer support platform
14+8%+17%0$1.7MSeed$1.6M, Sep 2021
54
The AI Underwriting OS for Commercial, Specialty & E&S insurance
167+7%+37%0$7.7MSeries A$7M, Nov 2025
55
Generative AI powered Shopify for home service professionals
168+7%+27%5$44MSeries B$27M, Aug 2025
56
Embedded lending infrastructure for software companies
95+7%−6%0$39.5MUndisclosed round$15M, May 2025
57
Scheduling and workforce management SaaS for home healthcare providers
32+7%+14%4$14.4MSeries A$10M, May 2025
58
GreaseBoss verifes industrial machinery is greased correctly
16+7% 0$1MSeed$1M, Mar 2021
59
Your AI GTM platform for In-Person Events
134+6%+19%5$2.4MSeed$2.2M, Mar 2021
60
Buy Now Pay Later + Cash Advance for Household Essentials
17+6%+89%0$175KYC investment$100K, Jan 2021
61
Making Restaurants more data-driven!
35+6%+13%0Pre-seed (before YC)Dec 2020
62
Marketplace for construction machines
19+6%+46%0$125KYC investment$125K, Mar 2021
63
Affordable insurance for the next billion Indians
39+5%−5%0$6.5MUndisclosed round$3.5M, Jan 2024
64
AI-powered video platform for Internal Comms and HR teams
20+5%+11%0$4.1MUndisclosed round$3.2M, Mar 2025
65
Slash commands anywhere
20+5% YC$3.3MSeed$3.3M, May 2021
66
The place where motivated investors and entrepreneurs co-own together.
42+5%+20%YC$20.5MSeries A$15M, Nov 2024
67
Easier and more reliable mobile app releases for teams.
21+5%+24%YC$2MSeed$2M, Jul 2022
68
Healthy organic food that creates a positive impact
21+5%+24%0
69
Leading online after-school for kids & teens to learn AI & coding
822+5%+18%9$2MUndisclosed round$1.2M, Jan 2023
70
Amazon-like logistics for e-commerce companies in Latam
248+5%+3%0$34MSeries A$1M, Feb 2025
71
Redcliffe Labs is India's Largest Omni-channel Diagnostics platform
2,065+5%+10%0$152MSeries C$42M, Sep 2024
72
The lightest electric aircraft motors in the world.
57+4%+21%0$24.6MSeries A$20M, Aug 2024
73
Online therapy platform for the Spanish-speaking market
146+4%+1%0SeedSep 2022
74
Energy Orchestration Platform
64+3%+2%1$17.2MSeries A$15M, Nov 2022
75
Marketing automation platform for selling to local businesses.
33+3% YC$5MSeed$5M, Jul 2024
76
GimBooks makes Bookkeeping Easy for small business owners
68+3%+11%0$125KNon-equity support$125K, Jan 2022
77
Aviron transforms workouts with game-based exercise machines, making…
73+3%+4%0$23.6MSeries A$18.6M, Feb 2022
78
Stocks and cryptos trading app with zero commissions and no minimums…
74+3%+4%YC$2MSeed$2M, Jul 2023
79
Stripe for online identity verification
42+2%+20%YC$8.7MSeries A$8.2M, Oct 2024
80
A growth automation platform for Amazon sellers
46+2%+12%0$7MSeries A$5M, Mar 2023
81
AI-powered customer service for startups
193+2%+9%0$1.2MUndisclosed round$125K, Jan 2023
82
Canada's digital health clinic for men
99+2%+5%8$38.9MSeries A$34.7M, Mar 2025
83
Digital bank for teenagers in LatAm connected to prepaid card
102+2%+3%0$25.8MUndisclosed round$10.7M, Apr 2023
84
Infrastructure and tools to build and scale blockchain applications.
110+2%−4%YC$102MSecondary$60M, Jan 2024
85
Simplifying hiring and payments for the global workforce
411+1%+4%0$34.7MSeries A$9M, Dec 2022
86
We underwrite and insure house rentals in Latam
131+1%−2%0$10MSeries A$5.6M, Nov 2024
87
We help US tech companies hire and manage software engineers in LATAM
4450%+9%0$18MSeries A$5M, Jan 2023
88
Challenger Bank for consumers in French speaking Africa.
3270%+4%0$49.1MDebt$1.5M, Aug 2026
89
Physical AI for asset-heavy industries
8880%+21%4$184MSeries C$120M, Dec 2024

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 W21 companies

How many YC W21 companies are there?

334 companies were in Y Combinator's Winter 2021 batch (W21); 226 are active.

Which YC W21 companies are hiring?

46 companies posted roles in the last 60 days, led by REGENT (30 roles), Shepherd (17 roles) and Codingal (9 roles). 77 mark themselves as hiring on YC's directory.

Which YC W21 companies are growing fastest?

By team growth over 6 months (10+ people): OpenCode (+200%), Venu AI (+58%) and Vapi (+50%).

Which YC W21 companies raised the most?

Largest latest rounds in the last 12 months, after their YC batch: Stoke Space ($1B), Nourish ($100M) and Ollama ($65M).

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