Microsoft’s open source journey: From 20,000 lines of Linux code to AI at global scale

Dive into Microsoft’s journey from its early days with the Linux kernel to its role in advancing AI technologies at scale.

Microsoft’s transformation into a prominent player within the open-source community has been remarkable. Once a sceptic, the company is now among the top contributors to this ecosystem. Over the last three years, Microsoft Azure has become the largest public cloud contributor and the second overall contributor to the Cloud Native Computing Foundation (CNCF). How did this shift happen? Let’s take a look at some key milestones along the way, showing how open-source technologies have become central to many of Microsoft’s flagship products, such as Microsoft 365 and the sophisticated AI workloads driving projects like OpenAI’s ChatGPT. Additionally, we’ve introduced several open-source initiatives, influenced by our experiences, which help foster innovation within the community.

Embracing Open Source: Key Milestones in Microsoft’s Journey

2009—A Fresh Start: 20,000 Lines to Linux. Back in 2009, Microsoft made a significant contribution of over 20,000 lines of code to the Linux kernel, primarily working on Hyper-V drivers under the General Public License, version 2 (GPLv2). While this wasn’t our initial step into the open-source realm, it marked a significant shift in our collaborative approach. By 2011, Microsoft ranked among the top five contributors to Linux, and today, 66% of customer workloads on Azure operate on Linux.

2015—Visual Studio Code: An Open Source Success. The introduction of Visual Studio Code (VS Code) in 2015 was a game-changer. This lightweight, open-source code editor is now beloved by millions, boasting more than 50 million monthly active developers. AI advancements have found a home here too, as we’ve rolled out the GitHub Copilot Chat extension as open source on GitHub, showing how AI can flourish in an open-source environment.

2018—Acquisition of GitHub and a Firm Commitment. The landmark acquisition of GitHub in 2018 underscored our dedication to open source and brought together a community of 28 million developers and 85 million repositories. As CEO Satya Nadella expressed, “Microsoft is all-in on open source… Our actions are the measure of our commitment.” According to GitHub’s 2024 Octoverse report, there are now 518 million public projects and over 1 billion contributions, with a remarkable 70,000 new generative AI projects added in just one year.

Open Source at Enterprise Scale: Powering the World’s Most Demanding Workloads

Modern cloud infrastructure relies heavily on open-source technologies such as Kubernetes and PostgreSQL. Kubernetes is now the second-largest open-source project, powering countless containerized workloads globally. Similarly, PostgreSQL stands out as one of the most popular relational databases. Services like Azure Kubernetes Service (AKS) and Azure’s managed Postgres harness these innovations, turning them into reliable, enterprise-ready offerings. This allows organisations to concentrate on innovation by minimising operational complexity.

COSMIC: Our expansive managed container platform plays a crucial role in transitioning Microsoft 365 to AKS containers. COSMIC manages millions of cores and stands as one of the largest AKS deployments globally. By embedding security and operational best practices, it significantly lowers engineering requirements and speeds up product delivery while managing costs. COSMIC efficiently utilises Azure’s resources and open-source technologies to function on a global scale, deploying tools such as Kubernetes event-driven autoscaling (KEDA) and Prometheus for real-time monitoring.

OpenAI’s ChatGPT: Built on Azure, ChatGPT effectively uses AKS for container management, Azure Blob Storage for user data, and Azure Cosmos DB for distributed data handling. With nearly 700 million weekly active users, it’s the fastest-growing consumer application ever. Remarkably, OpenAI operates this service with a small team of around 12 engineers, demonstrating the power of managed platforms like AKS. This allows for efficient scaling across over 10 million compute cores worldwide.

When you chat with ChatGPT, your input and conversation history are stored in an open-source database, specifically Azure Database for PostgreSQL. The AI can remember your context thanks to this setup. The model operates in containers across thousands of AKS nodes, with Azure Cosmos DB quickly replicating data for enhanced user experience. All of this is powered by open-source technologies, enabling ChatGPT to manage over a billion queries daily without significant operational strain.

What Azure Teams Are Building in the Open

At Microsoft, our dedication to open-source development drives our engineers to actively influence open-source infrastructures. Our philosophy is clear: contribute upstream first and integrate those innovations into our products. This commitment extends to collaborating with partners, customers, and even competitors in various upstream projects. Some notable contributions include:

• Dapr (Distributed Application Runtime): Launched by Microsoft in 2019, Dapr simplifies cloud-agnostic application development with modular building blocks.
• Radius: This CNCF Sandbox project aids developers in defining application services and dependencies across different platforms.
• Copacetic: A tool that allows developers to patch container images swiftly, facilitating quicker security updates.
• Dalec: A tool for creating secure OS packages and containers while generating software bill of materials (SBOMs).
• SBOM Tool: A command-line interface for generating open-source compliant SBOMs, enhancing transparency.
• Drasi: A tool that reacts to real-time data changes for dynamic workflows.
• Semantic Kernel and AutoGen: Frameworks aimed at developing collaborative AI applications.
• Phi-4 Mini: A compact AI model optimised for reasoning tasks, launched in 2025.
• Kubernetes AI Toolchain Operator (KAITO): An operator simplifying AI workload deployments across diverse environments.
• KubeFleet: Facilitates application management across multiple Kubernetes clusters

This is a brief overview of Microsoft’s involvement in open-source projects, all contributing valuable lessons learned from our global-scale operations, while inviting the community to collaborate.

Open Source + Azure = Empowering the Next Generation of Innovation

Microsoft’s adventure with open source has transformed immensely since that initial contribution to the Linux kernel back in 2009. Today, open-source solutions lie at the core of many Azure offerings. Our active contributions to projects like Kubernetes, KAITO, Dapr, and Radius drive open-source advancements forward. Each successful product, from Microsoft 365 to ChatGPT, ultimately hinges on robust platforms like AKS, underpinned by vibrant open-source communities.

Join Us at Open Source Summit Europe 2025

We’re thrilled to be participating in the upcoming Open Source Summit Europe 2025, taking place from August 25–27. Stop by our booth D3 for live demonstrations, engaging sessions on a variety of topics, and a chance to connect with our Open Source team. Don’t miss our conference presentations featuring insights and updates from our ongoing work in the open-source arena.

¹ TechRepublic, ChatGPT’s Rapid Growth: On Track For 700M Weekly Users, August 5, 2025.