Every time you install an extension in Cursor, AWS Kiro, Windsurf, or Google Antigravity, you are not hitting Microsoft’s Visual Studio Marketplace. You are hitting Open VSX — a vendor-neutral registry run by the Eclipse Foundation that most developers have never heard of, even though it is now their primary extension source. This week, with Open VSX at version 1.0 and Google signing on as a strategic sponsor, it is worth understanding the infrastructure your AI IDE depends on.
Why Microsoft’s Marketplace Is Off-Limits #
VS Code itself is MIT-licensed. The Marketplace is not. Microsoft’s Terms of Service for the Visual Studio Marketplace explicitly prohibit “alternative products built on a fork” from accessing it. That restriction is not accidental — it is intentional. When Cursor, Kiro, Windsurf, and others forked the open-source Code-OSS codebase to build AI-native editors, they inherited the code but lost access to the distribution channel. They needed somewhere else to send extension installs.
Open VSX was the answer. Started by GitPod in 2020 and later donated to the Eclipse Foundation, it implements its own API (Microsoft’s is proprietary and undocumented) and provides the same publisher-to-developer pipeline: a web UI, a CLI tool called ovsx
, and a registry that any compliant editor can point to. Extension parity is now substantial — roughly 90% of popular extensions are cross-published to both registries.
The 1.0 Milestone and What It Signals #
Open VSX 1.0.0 shipped June 24, 2026, focused on stability and security: read-only mode, TLS-protected Redis connections, and production hardening that the 300 million monthly download figure demands. The same month, Google joined the Eclipse Foundation as a Strategic Member specifically to sponsor Open VSX. AWS had already made the same bet in March, providing infrastructure and joining as a paying enterprise customer of the managed registry tier.
The numbers justify the attention. The registry serves over 300 million downloads per month, peaks at 200 million daily requests, and hosts 12,000+ extensions from 8,000+ publishers. The Managed Registry — launched in April 2026 with a 99.95% uptime SLA — counts AWS Kiro, Google Antigravity, and Cursor as its first enterprise customers. This is no longer a scrappy community project. It is infrastructure.
What Developers Actually Need to Know #
The practical gap matters. Microsoft’s own extensions are not available on Open VSX and never will be: Pylance, C# Dev Kit, C/C++ (ms-vscode.cpptools
), Live Share, and Remote SSH all stay behind the marketplace wall. If you are migrating a heavy Python or C# workflow from VS Code to Cursor or Kiro, plan for Pylance’s absence. There are alternatives — Pyright is solid, and most AI IDEs now bundle their own language intelligence — but the gap is real and occasionally painful.
There is also a security dimension that surfaced in January 2026: VS Code forks were recommending extensions by name that did not exist in Open VSX, leaving unclaimed namespaces open to supply chain attacks. The Eclipse Foundation responded with namespace verification measures, but the general rule stands: audit your extensions when switching registries, and check open-vsx.org before installing something unfamiliar.
Microsoft Accidentally Created the Infrastructure It Feared #
Here is the irony. By locking down the Visual Studio Marketplace, Microsoft forced every AI IDE builder to find an alternative. That pressure consolidated the entire ecosystem around Open VSX, turned the Eclipse Foundation into a critical infrastructure steward, and brought in Google and AWS as backers. VS Code’s marketplace share may still be large, but its growth trajectory has stalled: the Rust community’s annual survey showed VS Code usage falling from 61.7% to 51.6% over three years, while Zed surged from near-zero to 18.6%.
Open VSX is the connective tissue of that alternative ecosystem. Google’s Amanda Casari put it plainly: “Open registries, like Open VSX, are critical infrastructure which keep the global developer ecosystem open to everyone.” That is not marketing — it is an accurate description of what happens when 300 million monthly downloads run through a single registry that three of the world’s largest tech companies now depend on.
What to Do Now #
If you use Cursor, Kiro, Windsurf, or any Code-OSS fork: check whether the extensions you rely on are published to open-vsx.org. If a specific extension is missing, you can either use the ovsx
CLI to mirror it yourself (if the license permits) or contact the publisher to request cross-publishing. For extension authors: dual-publishing to both registries is now table stakes if you want your work to reach the full developer audience. The AI IDE era is here, and the audience that cannot reach you through Microsoft’s marketplace is growing every quarter.