Y Combinator Summer 2021 (S21) Companies

Sully builds medical AI software for healthcare providers, including ambient documentation, scheduling, intake, and clinical decision support tools designed to reduce administrative burden and improve patient care efficiency.

8 investors

Superwall provides a no-code platform for mobile app developers to design, A/B test, and optimize in-app paywalls and subscription flows. The platform enables monetization experiments and revenue optimization for iOS, Android, and cross-platform apps.

2 investors

Suplias is a business services platform that simplifies business operations across Africa. The company aims to reduce barriers to enterprise establishment and growth, thereby creating employment and improving living standards in the region.

1 investor

Swipe is a mobile-first invoicing and accounting platform that enables small businesses to create invoices, manage inventory, track payments, and send bills via WhatsApp, email, or SMS. The platform serves small businesses and merchants in India with simplified accounting and payment collection features.

2 investors

Synder provides automated accounting and bookkeeping software that integrates with payment platforms and e-commerce tools to simplify financial management for small businesses and e-commerce sellers. The platform automates transaction categorization, reconciliation, and revenue recognition for various accounting systems.

2 investors

TableVibe provides a commission-free online ordering platform and customer feedback system for restaurants to accept direct pickup and delivery orders and build customer relationships without relying on third-party delivery apps.

1 investor

Talentdrop provides a hiring platform that helps managers track and manage job referrals shared across social networks like LinkedIn, Slack, and Twitter in a centralized location.

2 investors

Talus develops a proprietary platform that measures and modulates the regulome—the body's gene expression control system—in native cellular contexts. The company designs AI-driven compounds and uses functional proteomics to enable drug discovery for transcription factors and regulatory proteins implicated in oncology, rare disease, and immune dysfunction.

5 investors

Monad is a security data pipeline platform that normalizes, filters, enriches, and routes security telemetry from any source to optimize SIEM costs and reduce alert noise for security teams.

1 investor

Tavus develops human-like AI agents called PALs that can see, hear, act, and understand in real-time, offering bespoke, fully-managed deployments for various enterprise workflows.

8 investors

Telivy provides continuous risk management and vulnerability monitoring for managed service providers (MSPs), combining asset monitoring, vulnerability prioritization, and automated remediation tracking aligned to security frameworks and CIS controls.

4 investors

Telmai is a data observability company that monitors and enhances data reliability for enterprise customers. The platform helps organizations ensure the quality and integrity of their data infrastructure.

4 investors

Tenyks develops a Visual Intelligence Platform that processes and extracts actionable insights from large collections of visual data and assets. The platform serves organizations seeking to convert visual data into strategic assets for decision-making and competitive advantage.

3 investors

testRigor provides AI-driven functional test automation for software development teams. The platform enables companies to achieve high test automation coverage with minimal maintenance effort, targeting fast-moving startups and development teams.

2 investors

The Breakaway provides performance coaching to cyclists through an AI-driven platform, with plans to expand to other sports and fitness disciplines.

2 investors

Therify is an in-network mental health platform that connects employees to licensed therapists, coaches, and wellness providers with guaranteed availability. The platform helps employers maximize employee wellbeing and reduce healthcare costs through faster access to care and reduced out-of-network utilization.

3 investors

TrackChain provides infrastructure with encrypted data transmission, single sign-on authentication, and automated backup systems for operational and financial information management.

1 investor

Titipku is an online marketplace connecting individual shoppers with traditional market vendors across Indonesia, offering fresh groceries including vegetables, fruits, meat, and daily essentials. The platform employs trained personal shoppers called "Jatiper" to fulfill orders from multiple market stalls with a single checkout and flexible same-day or next-day delivery.

1 investor

Toku provides software for Latin American businesses to manage accounts receivable operations, including payment processing, retry logic for failed transactions, and customer notifications, allowing companies to improve cash collection efficiency.

6 investors

TransAstra develops propulsion systems and telescope technology for space operations. The company's Omnivore propulsion system uses concentrated sunlight to power spacecraft with various propellants, while its Sutter Telescope System locates asteroids, orbital debris, and fast-moving objects for commercial and defense applications.

2 investors

Trii is a Colombian fintech platform that enables retail investors to access stock market investments in a user-friendly, affordable manner across Latin America. The company operates in three countries and serves over 600,000 active users seeking to democratize investment access.

3 investors

Truss Payments provides payment processing and financial services for builders and construction firms, including ACH and card payment acceptance, subcontractor payouts, corporate card issuance, and expense management.

3 investors

Tuli operates a network of UK pharmacies that function as diagnostic hubs, offering blood testing and clinical services directly to patients and healthcare providers through a simplified booking and sample collection process.

2 investors

Turion builds space infrastructure including vehicles, mission software, and payloads for tactical space operations, orbital logistics, and space domain awareness. The company operates satellites in orbit, offers mission planning software and constellation management, and is developing resource extraction technology for asteroid mining.

18 investors