Visual Studio Code
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Visual Studio Code (commonly VS Code) is a free, cross-platform source-code editor developed by Microsoft and announced at the Build conference on April 29, 2015 [1]. Built on the Electron framework around an MIT-licensed core, it became the most widely used development environment in the world within three years of launch and has topped every Stack Overflow Developer Survey since 2018, reaching 75.9 percent of respondents in 2025, its highest share ever [2][4]. Since 2021 it has also been the primary delivery vehicle for GitHub Copilot, and with it the central battleground of AI-assisted programming: the editor gained an autonomous agent mode and Model Context Protocol support in 2025, Microsoft open-sourced its Copilot Chat extension that June, and its codebase serves as the foundation for AI-native forks such as Cursor and Windsurf [13][16][22].
VS Code is a hybrid of open and proprietary software. The underlying project, "Code - OSS," is published on GitHub under the MIT license, while the branded binaries Microsoft distributes add telemetry, the product name, and a proprietary license [4]. The editor runs on Windows, macOS, and Linux, updates on a monthly release cadence, and is extended through the Visual Studio Marketplace, which hosts tens of thousands of extensions [4]. In May 2025 Microsoft announced that Visual Studio and VS Code together had passed 50 million monthly active developers [6].
Its dominance is most visible in Stack Overflow's annual surveys:
| Survey year | VS Code share | Note |
|---|---|---|
| 2018 | ~35% | First year ranked the most popular development environment [4] |
| 2019 | ~50% | Half of all respondents [4] |
| 2024 | 73.6% | Roughly five times the share of JetBrains IntelliJ [2] |
| 2025 | 75.9% | AI-native rivals debut: Cursor 18%, Claude Code 10%, Windsurf 5% [2] |
VS Code grew out of a failure. Erich Gamma, a co-author of the "Gang of Four" Design Patterns book and a lead of IBM's Eclipse platform, joined Microsoft in 2011 to build "Monaco," a browser-based editor used for editing Azure websites; it attracted only around 3,000 monthly users [3]. Gamma's team in Zurich pivoted the web technology into a desktop application, internally code-named "Ticino," by wrapping it in GitHub's Electron shell, which combines the Chromium rendering engine with Node.js [3][4].
The result was unveiled as Visual Studio Code on April 29, 2015, a free, cross-platform editor that surprised observers from a company whose flagship IDE ran only on Windows [1]. Microsoft published the source code under the MIT license on November 18, 2015, and added extension support the same month [4]. Version 1.0 shipped on April 14, 2016, by which point the editor already had half a million monthly active users [5].
Adoption then compounded: first place in the Stack Overflow survey by 2018, half of all developers by 2019, and roughly three quarters from 2021 onward [2][4]. A browser-only build, vscode.dev, launched in October 2021, and the same Monaco component powers GitHub Codespaces and github.dev [4]. GitHub retired its own Atom editor, the project for which Electron was originally created, in December 2022. By the editor's tenth anniversary in 2025, Microsoft counted more than 50 million monthly users across the Visual Studio family [6].
The desktop application is an Electron shell written largely in TypeScript, with the Monaco editor as its text-editing core [4]. Extensions run in a separate extension-host process, so a misbehaving extension cannot freeze the UI. Two protocols that VS Code introduced became industry standards: the Language Server Protocol (2016), which lets any editor reuse the same language-intelligence server, and the Debug Adapter Protocol. Remote-development extensions let the UI run locally while code, tools, and terminals execute in containers, on remote machines, or in the cloud.
The extension ecosystem is the platform's moat, and it is not fully open. The Visual Studio Marketplace's terms restrict its use to official Microsoft products, and several widely used extensions, including Pylance, the C/C++ extension, and the Remote Development pack, are proprietary and licensed only for genuine VS Code builds [20][21]. Because official binaries include telemetry, a community project, VSCodium, distributes builds of Code - OSS without Microsoft branding or telemetry, defaulting to the Eclipse Foundation's Open VSX registry for extensions instead of Microsoft's marketplace [7].
VS Code was the launch surface for GitHub Copilot, the first mass-market AI pair programmer. The technical preview arrived as a VS Code extension on June 29, 2021, powered by OpenAI's Codex model [8], and Copilot became a paid product in June 2022 [9]. Copilot Chat, a conversational sidebar, reached general availability in December 2023 [10]. In December 2024 Microsoft added a free Copilot tier directly into VS Code, with 2,000 completions and 50 chat requests per month and a choice between GPT-4o and Anthropic's Claude 3.5 Sonnet, making an AI assistant part of the default experience [11].
2025 turned the assistant into an agent. Agent mode, previewed in VS Code Insiders in February 2025, lets Claude-, GPT-, or Gemini-class models plan multi-step tasks, edit files across a codebase, run terminal commands, and iterate on compile and test errors until a task completes [12]. Microsoft described it as an "autonomous peer programmer" that "performs multi-step coding tasks at your command," analyzing the codebase, reading relevant files, proposing edits, and running terminal commands and tests [12]. It rolled out to all users in early April 2025 together with support for the Model Context Protocol, which lets agents call external tools and data sources; MCP support reached general availability in version 1.102 in July 2025 [13][14]. Agent mode is one expression of the broader AI coding agent category that VS Code now hosts directly.
At Build 2025 (May 19, 2025), Microsoft announced it would make VS Code "an open source AI editor," open-sourcing the GitHub Copilot Chat extension and folding its AI features into the editor's core [15]. The company argued that "AI experiences can thrive by leveraging the vibrant open-source community, just as VS Code has successfully done over the past decade," and that large language models had "significantly improved, mitigating the need for 'secret sauce' prompting strategies" [15]. The code was published under the MIT license on June 30, 2025, exposing the system prompts, context-gathering logic, and agent implementation that had been proprietary [16].
The editor has since become deliberately model- and agent-agnostic. GitHub's Agent HQ initiative, announced at GitHub Universe in October 2025, brings third-party coding agents from Anthropic, OpenAI, and later Google, Cognition, and xAI into GitHub and VS Code under a single Copilot subscription [17]. With version 1.109 (January 2026 release), Claude and Codex agent sessions run inside the editor alongside Copilot, tracked in a unified Agent Sessions view that Microsoft pitches as a "home for multi-agent development" [18]. Version 1.121 (May 2026) extended this to remote agent sessions running off the local machine [19].
| Date | Milestone |
|---|---|
| June 29, 2021 | GitHub Copilot technical preview ships as a VS Code extension [8] |
| June 21, 2022 | Copilot general availability (paid subscription) [9] |
| December 29, 2023 | Copilot Chat GA in VS Code and Visual Studio [10] |
| December 18, 2024 | Free Copilot tier built into VS Code [11] |
| February 2025 | Agent mode preview in VS Code Insiders [12] |
| April 7, 2025 | Agent mode for all users; MCP support in preview [13] |
| May 19, 2025 | "Open source AI editor" plan announced at Build [15] |
| June 30, 2025 | Copilot Chat extension code released under MIT [16] |
| July 2025 (v1.102) | MCP support generally available [14] |
| October 2025 | Agent HQ: third-party agents (Claude, Codex) in GitHub and VS Code [17] |
| January 2026 (v1.109) | Multi-agent sessions and Agent Sessions view [18] |
| May 2026 (v1.121) | Remote agent sessions [19] |
Because Code - OSS is MIT-licensed, anyone may fork it, and the most consequential AI coding startups did exactly that. Cursor, launched in 2023 by Anysphere, rebuilt the editor around AI-first completions and agents; by November 2025 the company had raised $2.3 billion at a $29.3 billion valuation, with Nvidia and Google among its investors [22]. Codeium shipped the Windsurf Editor, another VS Code fork marketed as the first "agentic IDE," in November 2024 and renamed the company Windsurf in 2025. After a roughly $3 billion acquisition agreement with OpenAI collapsed in July 2025, Google DeepMind hired Windsurf's CEO Varun Mohan and co-founder Douglas Chen in a $2.4 billion licensing-and-compensation deal, and Cognition, maker of Devin, acquired the remaining company days later [23]. In the 2025 Stack Overflow survey the forks registered real but far smaller shares than their parent: 18 percent for Cursor and 5 percent for Windsurf [2].
The forks inherit VS Code's interface and extension APIs but not its commercial ecosystem. Microsoft's marketplace terms have long barred non-Microsoft products from downloading extensions, a rule Cursor reportedly worked around by proxying marketplace requests [20][21]. In April 2025 Microsoft began enforcing the boundary technically: version 1.24.5 of its C/C++ extension added environment checks that disabled it inside Cursor and VSCodium, and similar restrictions already applied to Pylance and Remote Development [21]. One developer told The Register they had asked the US Federal Trade Commission to examine the practice as self-preferencing; Microsoft noted the license terms had existed for years [21]. The practical effect was to push forks toward the open Open VSX registry, which Cursor adopted as its extension source [20].
Microsoft's counter-strategy has been to give away and open up rather than wall off: a free Copilot tier (December 2024), open-sourcing Copilot Chat (June 2025), and hosting rival agents inside the editor (2025 to 2026) [11][16][17]. As of June 2026 the contest is unresolved; VS Code's survey share keeps rising even as Cursor's revenue and valuation grow.
VS Code is the closest thing modern software development has to a common substrate. Its Monaco component powers browser IDEs across the industry, the Language Server Protocol it introduced decoupled language tooling from any single editor, and its extension model defined how a code editor becomes a platform [4]. For Microsoft, an editor that began as a pivot from a failed web product became the company's distribution channel for GitHub Copilot, placing an AI assistant in front of tens of millions of developers by default [6][11].
The same openness that built that audience also armed Microsoft's competitors: Cursor and Windsurf demonstrate that a permissively licensed editor can be forked into multibillion-dollar rivals [22][23]. The resulting dynamic, free AI features and an open-sourced Copilot on one side, marketplace and extension restrictions on the other, has made VS Code both the prize and the weapon of the AI editor wars [16][21].