Y Combinator Summer 2021 (S21) Companies

Repool provides software and services for launching and administering hedge funds, helping managers comply with securities regulations.

1 investor

REPROSENT captures patient treatment experience data to support dose, safety, and development decisions in oncology and advanced cancer therapies. The platform operates as a lightweight, non-interventional overlay on existing clinical trials and care programs, converting patient symptoms into structured, computable signal for development and clinical teams.

1 investor

Revery AI operates a social platform where fashion creators showcase designs and build audiences, powered by AI tools that generate product images and create virtual try-on capabilities for styling outfits on different models.

1 investor

Revolve develops a surgical robotics platform with 5mm wristed instruments and zero-footprint design for operating rooms, enabling digital surgery at costs comparable to laparoscopy. The system is designed for access across independent outpatient centers and large health networks.

1 investor

Rinse combines technology and hospitality with science-based dental care to provide preventive oral health services through modern studio experiences. It aims to modernize dentistry by addressing fragmented industry practices and outdated approaches.

3 investors

Rivia.ai provides a platform for creating and distributing interactive product demonstrations that SaaS companies can embed in websites, email, and advertising. Marketing and sales teams use the tool to quickly produce guided demos that allow prospects to explore products independently.

1 investor

RMFG provides custom sheet metal parts and assemblies manufactured in the United States, targeting product makers and manufacturers seeking domestic production alternatives. The company combines human expertise with proprietary software and hardware technology to offer faster turnaround and lower costs than comparable overseas manufacturing.

2 investors

Rootly provides an on-call and incident management platform for mid-to-large technology companies.

3 investors

Ruta Health is a digital platform that connects patients with licensed doctors to receive personalized health information asynchronously. The service addresses the gap between unreliable internet searches and generic symptom checkers by providing one-on-one medical guidance tailored to individual health questions.

1 investor

Ruth Health offers remote pelvic floor therapy sessions for postpartum people experiencing incontinence or prolapse, with the goal of helping them return to normal activities more quickly.

1 investor

SafeBeat uses engineering and machine learning to develop solutions for cardiac care and arrhythmia management. The company serves cardiologists, electrophysiologists, and healthcare organizations.

1 investor

Safer Management provides attendance tracking software to public school districts and colleges that helps schools accurately capture daily attendance data for federal funding purposes.

1 investor

SalaryBook provides a mobile application that handles payroll processing, employee attendance tracking, and expense management for Indian small and medium-sized businesses. The platform also enables blue-collar workers to build online credit and skills profiles.

2 investors

SalaryBox provides a mobile app platform for small businesses to manage payroll and staff operations. The company serves small enterprises with payroll management and employee data insights.

5 investors

Satsuma provides infrastructure for developers to extract, transform, and query blockchain data from multiple networks via APIs. The platform addresses the technical challenge of accessing distributed ledger information for web3 application development.

1 investor

Scispot provides automated sample tracking and traceability software for laboratory environments, replacing manual processes and spreadsheets with end-to-end logging and monitoring capabilities. The platform serves laboratories and research facilities seeking to improve sample management and ensure compliance.

1 investor

ScratchDB provides automated database management for analytics, handling tasks like server setup, data import, querying, replication, and sharding without manual configuration.

1 investor

Secoda is an AI-powered data management platform that consolidates data catalog, lineage, governance, monitoring, and observability functions for enterprises. It enables data teams and business stakeholders to access and act on insights from their organization's data infrastructure.

4 investors

A desktop application that provides in-game coaching and post-game analysis to PC gamers through an overlay and voice assistant, using computer vision to deliver real-time feedback and recommendations.

1 investor

Sensible Biotechnologies develops a cell-based mRNA design and manufacturing platform that produces pure, low immunogenicity mRNA therapeutics for drug development. The platform addresses limitations of synthetic mRNA by enabling design-based biology approaches.

5 investors

Sentiyen develops AI assistants that learn from a company's proprietary content to answer customer questions at scale. The platform serves creators and businesses seeking to automate customer support and sales conversations.

2 investors

Sequin AI develops AI voice agents designed to handle collections calls for consumer lenders and loan servicers, with built-in compliance safeguards.

1 investor

SFA Therapeutics develops oral therapeutic candidates based on deuterated short-chain fatty acids to treat autoimmune and oncologic diseases. The company's lead program, SFA-002, is in Phase 2 development for plaque psoriasis, with additional pipeline assets targeting pancreatic cancer, liver cancer, rheumatoid arthritis, and inflammatory bowel disease.

4 investors

Shape uses natural language processing to make data exploration and analytics more accessible by answering specific data questions without requiring traditional dashboard interfaces. The platform serves analysts and decision-makers across projects who need fast, flexible data retrieval.

1 investor