Y Combinator
Open-source Y Combinator companies
The platform for building and operating time series applications.
210 people · New York City, NY, USA · Analytics, Open Source, Time Series, Databases · YC page
Software development platform.
201 people · San Francisco, CA, USA · Open Source, DevOps, Enterprise Software · YC page
Apollo helps engineering teams accelerate delivery
200 people · San Francisco, CA, USA · Developer Tools, Open Source, GraphQL · YC page
The single platform to analyze, test, observe, and deploy new features
150 people · San Francisco, CA, USA · Developer Tools, Open Source · YC page
Protocol Labs makes internet protocols: IPFS, Filecoin, and more.
130 people · San Francisco, CA, USA · Crypto / Web3, Open Source · YC page
Conversational Voice and Multimodal AI built with Open Source
126 people · San Francisco, CA, USA · Developer Tools, Open Source, AI, AI Assistant · YC page
Secure Collaboration for Technical Teams
120 people · San Francisco, CA, USA · DevSecOps, Collaboration, Security, Open Source · YC page
Build in a weekend. Scale to millions.
120 people · San Francisco, CA, USA · Developer Tools, Open Source, Big Data, Data Engineering · YC page
Frontend Platform for eCommerce
100 people · Warsaw, Masovian Voivodeship, Poland · Developer Tools, Open Source, E-commerce · YC page
Context layer for production-grade AI agents
90 people · San Francisco, CA, USA · Developer Tools, Open Source, Data Engineering, AI · YC page
Security infrastructure for developers and agents
70 people · San Francisco, CA, USA · Developer Tools, Security, Open Source · YC page
Open source feature flagging and A/B testing
46 people · San Francisco, CA, USA · Developer Tools, Analytics, Open Source · YC page
Connect, Unify, Respond to any data, anywhere with human-level…
41 people · San Francisco, CA, USA · Developer Tools, Machine Learning, Open Source, Enterprise Software · YC page
Open source alternative to DataDog
38 people · San Francisco, CA, USA · Developer Tools, Open Source · YC page
Observability and Governance for AI-Generated Python scripts.
35 people · Campinas, SP, Brazil · Developer Tools, Open Source, Infrastructure, AI · YC page
Open-source, serverless vectordb for production-scale generative AI
35 people · San Francisco, CA, USA · AIOps, Machine Learning, Open Source, Data Engineering · YC page
Open Source Infrastructure for the Financial Internet
33 people · Paris, Île-de-France, France · Developer Tools, Fintech, Payments, Open Source · YC page
Authorization Infrastructure securing AI at OpenAI, Zoom, & more
31 people · New York City, NY, USA · Developer Tools, Security, Open Source, Data Engineering · YC page
The Javascript framework for building AI agents, from the Gatsby devs
30 people · San Francisco, CA, USA · Developer Tools, Open Source, AI · YC page
Cloud Development Environments with one click
30 people · San Francisco, CA, USA · Developer Tools, Open Source, Kubernetes · YC page
Shift FinOps Left: Proactively Find & Fix Cloud Cost Issues
25 people · Remote · Developer Tools, DevSecOps, FinOps, Open Source · YC page
The open source AI coding agent
24 people · Toronto, ON, Canada · Developer Tools, Open Source · YC page
The open source Looker alternative
23 people · London, England, United Kingdom · Developer Tools, Analytics, Open Source, Data Visualization · YC page
Call every LLM API like it's OpenAI [100+ LLMs]
20 people · San Francisco, CA, USA · AIOps, Developer Tools, Generative AI, Open Source · YC page
API first electronic health record (EHR) that is open source
20 people · San Francisco, CA, USA · Developer Tools, Open Source, Healthcare · YC page
The open-source document editor for humans and AI agents.
20 people · Berlin, Berlin, Germany · Developer Tools, Open Source, AI · YC page
Icons and social logos for your website.
17 people · Bentonville, AR, USA · Developer Tools, Design Tools, Open Source · YC page
Build and deploy fully‑managed AI agents and workflows
17 people · London, England, United Kingdom · Developer Tools, Open Source, AI · YC page
Database for AI
15 people · San Francisco, CA, USA · Computational Storage, Deep Learning, Generative AI, Computer Vision · YC page
Open-source data observability for data teams
12 people · Tel Aviv-Yafo, Tel Aviv District, Israel · Developer Tools, Analytics, Open Source, Data Engineering · YC page
Open data platform for traceable, multimodal AI
12 people · Developer Tools, Machine Learning, Biotech, Open Source · YC page
Enterprise ready webhooks service, open-source and in the cloud
12 people · San Francisco, CA, USA · Developer Tools, Open Source, API · YC page
Open-Source Reinforcement Learning (RL) & Fine-tuning for LLMs.
12 people · San Francisco, CA, USA · Developer Tools, Generative AI, Open Source, Infrastructure · YC page
Open-source, self-hosted, session replay tool for developers.
11 people · New York City, NY, USA · Developer Tools, Open Source · YC page
You should just use Postgres.
11 people · San Francisco, CA, USA · Developer Tools, Analytics, Open Source, Infrastructure · YC page
Open Source AI Agent to automate browser workflows via an API
11 people · San Francisco, CA, USA · Robotic Process Automation, Workflow Automation, Open Source, API · YC page
The Operating System for Edge Computing
11 people · San Francisco, CA, USA · Developer Tools, Open Source · YC page
Open-source, AI-first and no-code business automation tool
10 people · San Francisco, CA, USA · Workflow Automation, Open Source, No-code, Enterprise Software · YC page
The Memory layer for AI Agents
10 people · San Francisco, CA, USA · Developer Tools, Generative AI, Open Source, Infrastructure · YC page
Open-source Retool for enterprise
10 people · San Francisco, CA, USA · Developer Tools, Open Source, Web Development · YC page
The operating system for building mission-critical enterprise apps.
10 people · San Francisco, CA, USA · Developer Tools, Open Source, Web Development, Infrastructure · YC page
Open source alternative to Auth0 / AWS Cognito / Firebase Auth
10 people · San Francisco, CA, USA · Developer Tools, Open Source · YC page
Plan and review AI generated code
10 people · London, England, United Kingdom · Machine Learning, Open Source, AI · YC page
Pipekit scales data & CI pipelines for enterprises
9 people · Remote · Developer Tools, Open Source, Data Engineering, DevOps · YC page
Automation Foundation Models For Tiny Devices
8 people · San Francisco, CA, USA · Developer Tools, Hard Tech, Open Source, AI · YC page
Webhooks Gateway for outgoing and incoming webhooks.
8 people · London, England, United Kingdom · Developer Tools, Open Source · YC page
The LLM Eval and Observability Platform for AI Quality
7 people · San Francisco, CA, USA · Developer Tools, Generative AI, Open Source, AI · YC page
The orchestration platform for teams who ship.
7 people · New York City, NY, USA · Developer Tools, Open Source, Infrastructure · YC page
Automated WireGuard networks for distributed systems and Kubernetes
7 people · Austin, TX, USA · DevSecOps, Next-gen Network Security, Open Source, Kubernetes · YC page
Open-source platform to turn scripts into internal apps & workflows
7 people · Paris, Île-de-France, France · Developer Tools, Workflow Automation, Open Source · YC page
The fastest & most scalable graph-vector database on the market
6 people · London, England, United Kingdom · Developer Tools, Open Source, Infrastructure, AI · YC page
A single API for all your integrations
6 people · San Francisco, CA, USA · Developer Tools, Open Source, API · YC page
connect, migrate and implement enterprise systems
6 people · BY, Germany · Open Source, API, Enterprise, Enterprise Software · YC page
Autonomously scaling environments
6 people · San Francisco, CA, USA · Developer Tools, Generative AI, Reinforcement Learning, Open Source · YC page
Open-source framework for building serverless applications
6 people · Zagreb, Croatia · Developer Tools, Open Source · YC page
The complete production quality platform. AI-powered E2E testing,…
5 people · Limerick, County Limerick, Ireland · Developer Tools, Open Source, DevOps · YC page
AI-Native Cloud Platform
5 people · New York City, NY, USA · Developer Tools, Open Source, Cloud Computing, AI · YC page
Cloud infrastructure for MCP servers and Claude / ChatGPT plugins.
5 people · ZH, Switzerland · Developer Tools, Open Source, Infrastructure, AI · YC page
Rivet Actors are the primitive for stateful workloads
5 people · San Francisco, CA, USA · Open Source, Infrastructure · YC page
Fastest inference anywhere: open models on-prem, hosted or on-device
5 people · San Francisco, CA, USA · Developer Tools, Open Source, Infrastructure, AI · YC page
API for unlimited, durable, real-time streams
5 people · San Francisco, CA, USA · Developer Tools, Open Source, API, Infrastructure · YC page
The authentication framework for TypeScript
4 people · San Francisco, CA, USA · Developer Tools, Security, Open Source · YC page
The cheapest, fastest inference cloud
4 people · San Francisco, CA, USA · Open Source, Infrastructure, AI · YC page
Full-service web, mobile, & cloud studio providing professional…
4 people · Austin, TX, USA · Open Source, Web Development, Cloud Computing · YC page
Stackup helps businesses manage their crypto assets.
4 people · Los Angeles, CA, USA · Developer Tools, Crypto / Web3, Open Source · YC page
Open Source AI Agent Improvement Platform
4 people · San Francisco, CA, USA · Developer Tools, Open Source, Infrastructure, AI · YC page
Open source applied AI lab building next-gen devtools
3 people · San Francisco, CA, USA · Developer Tools, Open Source, AI · YC page
Give every agent a cloud desktop
3 people · San Francisco, CA, USA · Open Source · YC page
Building the library for superintelligence.
3 people · San Francisco, CA, USA · Developer Tools, Open Source, AI · YC page
Easiest way to set up Zero Trust Access for your team
3 people · San Francisco, CA, USA · DevSecOps, Next-gen Network Security, Security, Open Source · YC page
Cursor for data analysis
3 people · New York City, NY, USA · Developer Tools, Analytics, Open Source, Data Science · YC page
Production infrastructure on autopilot
3 people · San Francisco, CA, USA · Developer Tools, Open Source, Infrastructure · YC page
Optimize performance on GPUs - 10x faster
3 people · New York City, NY, USA · Developer Tools, Hardware, Open Source, AI · YC page
Open networking and security for your workforce, AI agents, and infra
3 people · New York City, NY, USA · Security, Open Source, Enterprise Software, Networks · YC page
Helping humans and AI agents understand massive codebases
3 people · San Francisco, CA, USA · Developer Tools, Open Source, AI · YC page
The makers of Klex Bots, your own team of digital coworkers.
3 people · Developer Tools, Open Source, AI · YC page
Agent swarms that make long-running tasks exponentially faster
2 people · London, England, United Kingdom · Swarm AI, Open Source · YC page
Let your teams' coding agents message each other
2 people · San Francisco, CA, USA · Developer Tools, Swarm AI, Open Source, AI · YC page
The fastest native app for agentic engineering.
2 people · San Francisco, CA, USA · Developer Tools, Open Source, AI · YC page
OpenRouter for Integrations
2 people · New York City, NY, USA · Developer Tools, Workflow Automation, Open Source, Personalization · YC page
Open-source monitoring for machine learning models
2 people · London, England, United Kingdom · Developer Tools, Machine Learning, Open Source · YC page
Run open models as fast as your hardware allows
2 people · San Francisco, CA, USA · Developer Tools, Open Source, Infrastructure, AI · YC page
Cloud Native SIEM (alternative to Splunk/Elastic)
2 people · Seattle, WA, USA · DevSecOps, Analytics, Open Source, Cybersecurity · YC page
Open source background agents
2 people · Singapore, Singapore · Open Source, AI · YC page
Self-optimizing neocloud that cuts LLM costs by 100x
2 people · San Francisco, CA, USA · Open Source, AI, ML · YC page
AI tooling
2 people · Berlin, Berlin, Germany · Open Source, AI · YC page
The open source Postman alternative.
2 people · San Francisco, CA, USA · Developer Tools, Open Source, API · YC page
Make software self-healing
2 people · Paris, Île-de-France, France · Developer Tools, Open Source, Kubernetes, Enterprise Software · YC page
Configuration language for building enterprise web apps 10x faster
2 people · Zagreb, Croatia · Developer Tools, Open Source · YC page
The Approval Layer for AI Agents
2 people · London, England, United Kingdom · Open Source · YC page
Caveman cuts what AI agents cost without making them dumber.
1 person · Amsterdam, NH, Netherlands · Developer Tools, Open Source, Infrastructure, AI · YC page
On-device Knowledge Graph engine for Enterprise Software
1 person · San Francisco, CA, USA · Developer Tools, Open Source · YC page
Catch bugs that code review tools miss
1 person · San Francisco, CA, USA · Developer Tools, Open Source, Enterprise, DevOps · YC page
Get up and running with large language models.
San Francisco, CA, USA · Developer Tools, Open Source, AI · YC page
Data platform for mission-critical real-time workloads
London, England, United Kingdom · Developer Tools, Analytics, Open Source, Time Series · YC page
Random labs is building long running autonomous coding agents.
San Francisco, CA, USA · Developer Tools, Open Source, AI, AI Assistant · YC page
Remote Shell Access in the Browser
San Francisco, CA, USA · Open Source · YC page
A complete DevOps platform delivered as a single application.
2000 people · San Francisco, CA, USA · Developer Tools, DevSecOps, Open Source · YC page
Open source tools of modern distributed systems.
150 people · San Francisco, CA, USA · Open Source, DevOps · YC page
Modern user-focused observability built on OpenTelemetry
62 people · Los Angeles, CA, USA · Open Source, Data Engineering, AI · YC page
Real-time. Big data. PostgreSQL
45 people · San Francisco, CA, USA · Open Source, Big Data, Databases · YC page
Run machine learning models in the cloud
36 people · San Francisco, CA, USA · Developer Tools, Machine Learning, Community, Open Source · YC page
Instantly offer SDKs and API Docs
30 people · New York City, NY, USA · Developer Tools, Open Source, API · YC page
Open source LLM engineering platform
26 people · Berlin, Berlin, Germany · Developer Tools, Generative AI, Analytics, Open Source · YC page
Spark-on-Kubernetes Data Engineering Platform
25 people · Paris, Île-de-France, France · Open Source, Data Engineering · YC page
Open-Source Postman alternative
19 people · San Francisco, CA, USA · Developer Tools, Open Source, API · YC page
Bun is an incredibly fast all-in-one JavaScript toolkit
13 people · San Francisco, CA, USA · Developer Tools, Open Source · YC page
The open source database for the realtime web.
11 people · San Francisco, CA, USA · Open Source · YC page
CodeStream is a Developer Collaboration Platform designed to…
10 people · New York City, NY, USA · Developer Tools, Collaboration, Open Source · YC page
Know what your LLM is doing — and why it’s failing
9 people · Tel Aviv-Yafo, Tel Aviv District, Israel · Developer Tools, Generative AI, Open Source · YC page
The open source, fullstack monitoring platform: stop guessing why…
8 people · Seattle, WA, USA · Developer Tools, Open Source, Monitoring · YC page
All-in-one API for search, RAG, & recommendations
7 people · San Francisco, CA, USA · Developer Tools, Open Source, API, Search · YC page
Serverless Analytics on Postgres
6 people · San Francisco, CA, USA · Developer Tools, Analytics, Open Source, Data Engineering · YC page
Fig adds visual apps, shortcuts, and autocomplete to your terminal.
5 people · San Francisco, CA, USA · Developer Tools, DevSecOps, Open Source · YC page
Open source GenAI development platform
5 people · Remote · Developer Tools, Generative AI, Open Source, AI · YC page
LLM Observability for Developers
5 people · San Francisco, CA, USA · AIOps, Developer Tools, Analytics, Open Source · YC page
The open-source AIOps platform
5 people · Tel Aviv-Yafo, Tel Aviv District, Israel · Open Source, Monitoring · YC page
Making APIs Developer-friendly
5 people · New York City, NY, USA · Developer Tools, Open Source · YC page
Open source continuous profiling software to debug performance issues
5 people · San Francisco, CA, USA · Developer Tools, Open Source, Kubernetes · YC page
Open-source, dev-friendly observability.
4 people · San Francisco, CA, USA · Developer Tools, Open Source, Infrastructure · YC page
Open Source Embedded Product Integrations
4 people · Remote · Developer Tools, Open Source, AI · YC page
Developer-First Headless CMS and Application Framework
3 people · Grand Rapids, MI, USA · Developer Tools, Open Source, API · YC page
Open source Voice AI
3 people · San Francisco, CA, USA · Developer Tools, Generative AI, Open Source, Conversational AI · YC page
Authorization and access control as a service.
3 people · Los Angeles, CA, USA · Developer Tools, Open Source, API · YC page
Cloud-native stream processing
2 people · San Francisco, CA, USA · Developer Tools, Open Source, Cloud Computing · YC page
Open source tools & services for reliable AI Agents & AI Applications
2 people · San Francisco, CA, USA · AIOps, Developer Tools, Generative AI, Open Source · YC page
The only database you'll ever need
2 people · Toronto, ON, Canada · Open Source, Databases · YC page
Turn expensive prompts into cheap fine-tuned models
2 people · Seattle, WA, USA · AIOps, Open Source, AI · YC page
Fast, native ETL for Postgres 🐘 🚀
2 people · Developer Tools, Open Source, Data Engineering, Enterprise Software · YC page
Open-source time-series data analytics extension for PostgreSQL
2 people · Los Angeles, CA, USA · Open Source, Time Series · YC page
Build Backends. Fast.
12 people · London, England, United Kingdom · Developer Tools, Open Source, DevOps, AI · YC page
The open source platform for managing identity in business software
5 people · San Francisco, CA, USA · Developer Tools, Security, Open Source, API · YC page
Open-source, customizable, headless CMS
5 people · San Francisco, CA, USA · Open Source · YC page
An Open Source dependency security tool that is smarter than the rest
4 people · Seattle, WA, USA · Developer Tools, DevSecOps, Security Orchestration, Automation and Response (SOAR), Security · YC page
AI agent that generates unit and integration tests
4 people · San Francisco, CA, USA · Developer Tools, Open Source, AI · YC page
Open source version control for metadata
3 people · San Francisco, CA, USA · Developer Tools, Analytics, Open Source, Data Engineering · YC page
Postgres vector database extension to build AI applications
3 people · San Francisco, CA, USA · Open Source, Enterprise, AI, Databases · YC page
Operating System for server-side apps
2 people · Vienna, Vienna, Austria · Developer Tools, Open Source · YC page
Open Source Data Observability
2 people · San Francisco, CA, USA · Developer Tools, Open Source, Data Engineering · YC page
Open source build tool for monorepos and large codebases
2 people · Portland, OR, USA · Developer Tools, Productivity, Open Source, Enterprise · YC page
Daily productivity tracker
2 people · San Francisco, CA, USA · Developer Tools, Open Source, Infrastructure, AI · YC page
Open-source library discovery
San Francisco, CA, USA · Developer Tools, DevSecOps, Open Source · YC page
FAQ
How many Y Combinator companies are open source?+
142 YC dev-tool companies are tagged open source in YC's directory (snapshot of 2026-10-20); 97 are active. Only companies that launched publicly on YC's site count.
Which YC batches have the most open-source companies?+
Winter 2023 (W23): 19; Winter 2021 (W21): 11; Summer 2022 (S22): 10.
Is every company here fully open source?+
They are tagged "Open Source" on YC's directory, which usually means an open-source core with a hosted or enterprise paid plan. Check each project's license before you build on it.
More: all YC dev-tool companies · open-source tools on DevHunt · free and open-source alternatives.
Source: Y Combinator's public company directory via the unofficial mirror yc-oss/api. DevHunt is not affiliated with Y Combinator.