Y Combinator Summer 2021 (S21) Companies

Shimmer provides coaching, community, and digital tools designed specifically for people with ADHD, combining expert guidance with peer support to help them reach their potential. The platform serves neurodivergent individuals seeking ADHD-specific support outside traditional mental health systems.

2 investors

ShipBlu is an AI-powered logistics platform that provides shipping, delivery, and fulfillment services for eCommerce businesses in Egypt. The platform offers instant cash payouts, real-time tracking, delivery verification, and integrated billing to streamline the shipping process.

1 investor

Siglo is a prepaid internet service provider in Mexico offering flexible, month-to-month internet access with download speeds up to 100 Mbps. The service uses modern network equipment and can be recharged via mobile app or at major retail locations.

4 investors

SigmaOS is a macOS web browser that organizes tabs into workspaces and includes AI-powered features like website summarization and contextual search. It targets students, founders, and creatives seeking improved productivity and focus.

2 investors

SIRKA is Indonesia's first metabolic clinic offering personalized weight management and health treatment through online consultations and in-clinic visits, with medications delivered directly to patients' homes. The service targets individuals seeking professional weight loss and metabolic health management with expert medical supervision.

3 investors

Sitenna provides infrastructure asset management software that centralizes asset data and integrates communications, contracts, and workflows across the asset lifecycle for infrastructure managers and asset management teams.

2 investors

Slash provides enterprise-grade cash management and deposit insurance services for businesses, offering FDIC coverage expanded across a network of partner banks with real-time transaction controls and approval workflows.

3 investors

Sleek provides AI agents that understand and interact with webpages to help users find and apply coupons, view cashback deals, and access product-level pricing information across millions of retailers. The platform serves digital commerce platforms, browser extensions, and app builders seeking to monetize through deal discovery and cashback rewards.

4 investors

Slope provides a B2B payments platform that enables businesses to accept payments and offer financing, with a focus on digitizing the order-to-cash process for online commerce. The company uses generative AI to modernize traditionally manual B2B payment workflows.

4 investors

A nutrition tracking app that uses computer vision AI to identify foods from photos and automatically log their nutritional information. The app serves consumers managing their diet and fitness goals.

2 investors

Soco is a visual AI platform that retrieves product recommendations in response to user queries, allowing shoppers to browse hundreds of items through conversational interaction.

1 investor

SolarMente finances residential solar panels, battery storage, and heat pump installations for homeowners in Southern Europe, with customers paying through monthly savings rather than upfront capital.

1 investor

Spark Studio makes an AI conversational partner that helps children practice English speaking through voice interaction. The tool targets students in non-English dominant countries who have classroom exposure to English but lack confidence in real conversation.

3 investors

A platform that aggregates and compares prices for the same products across different online retailers, helping shoppers identify lower-cost purchase options.

3 investors

Sproutfi is a Latin American investment platform that lets users buy US stocks and ETFs with minimal capital requirements and no fees, while connecting investors through social features for idea-sharing and learning.

1 investor

Squire is a developer tool that generates pull request descriptions, conducts code reviews, and writes code to address feedback from reviews.

1 investor

Stardex is an AI-first applicant tracking system (ATS) and customer relationship management (CRM) platform designed for recruiting and staffing firms. The software combines semantic search, autonomous agents, and workflow automation to help recruiters source candidates from their database and manage placements more efficiently.

1 investor

Stepful provides affordable, online healthcare education programs with live instruction and personalized coaching to train students for healthcare careers. The company targets individuals seeking to enter the healthcare workforce and aims to address systemic shortages in medical staffing.

6 investors

Stipop is a platform that enables independent character creators to earn revenue directly from their audiences through digital features. The company previously operated as a sticker marketplace and continues to distribute stickers through partnerships with major software platforms while offering API and SDK tools to app developers.

4 investors

Storylane is a demo automation platform that helps sales and marketing teams build interactive product demos and conversational AI agents across websites, campaigns, and sales calls to qualify and convert buyers throughout the sales cycle.

2 investors

StowNest provides storage space solutions for both personal and business customers, offering short-term and long-term storage with warehouse-level quality of service. The platform targets urban residents and SMEs seeking affordable, technology-enabled storage management.

1 investor

StrideQ provides an AI-powered phone answering and catering ordering system for restaurants, handling phone orders and catering inquiries without dedicated staff or new hardware. It aims to reduce missed calls, cut labor costs, and increase orders during peak hours.

1 investor

Strive Math teaches coding and mathematics to children aged 8-16 through interactive courses and 1-1 classes, with a focus on developing problem-solving and critical thinking skills. The company also provides digital tools to support teachers in delivering engaging STEM learning experiences.

1 investor

A video platform and online community where students connect with peers globally to study in real time, with tools designed to increase focus and reduce isolation.

3 investors