How this works: a .vsix package is a plain ZIP archive. This page reads it directly in your browser tab — unzipping it, parsing extension.vsixmanifest and the extension's own package.json — and never uploads the file anywhere.
Why check first: installing an extension from the Marketplace goes through Microsoft's own review, but a .vsix downloaded from a GitHub release, a mirror, or sent to you directly skips that. This page lets you see what an extension actually registers — what commands it adds, what settings it defines, whether it wants to activate on every file or something specific — before you trust it enough to run code --install-extension.
Troubleshooting
My file won't open at all
A .vsix is a ZIP archive with an extension.vsixmanifest file at its root. If this page can't find that file, either the archive isn't actually a VSIX package, or it's corrupted — try re-downloading it.
"What it registers" section is missing
That section is built from the extension's own package.json, referenced by the manifest. If that file is missing or isn't valid JSON, this page shows a note explaining why and still displays everything else it could read.
Can I install the extension from here?
No — this page only inspects the package. To install it, use VS Code's own Extensions view ("Install from VSIX…") or code --install-extension yourfile.vsix on the command line.