AsyncAPI Preview

Preview AsyncAPI documents inside VSCode.

AsyncAPI Preview was simplified and reworked from scratch to use the latest @asyncapi/asyncapi-react, removing old dependencies on Express, socket.io and js-yaml with better startup performance and bundle size.

You can open AsyncAPI Preview from the editor title/context menu. (If you don't see that button, you can use shift+command+P to open command palette and select Preview AsyncAPI)

Web Extension Compatibility

The extension now runs in the web version of VS Code i.e. directly in your browser on vscode.dev, github.dev, gitlab.com/-/ide, gitpod.io, and other cloud development environments, as well as a local browser host for development.

Key Benefits

• No install required: open a repo in your browser and preview AsyncAPI files without a desktop VS Code.
• Works on vscode.dev, github.dev, GitLab Web IDE, Gitpod & more: perfect for quick reviews during PRs or exploring examples.
• Consistent experience: same preview workflow on desktop and web.

Usage

A) On vscode.dev / github.dev

1. Open your repo:
   • https://vscode.dev/github// (or use the . keyboard shortcut on GitHub to open github.dev).
2. Install AsyncAPI Preview in that browser session (Command Palette → "Extensions: Install from VSIX…" if you're side-loading, or from Marketplace once the web-ready version is published).
3. Open an *.yaml / *.yml (or JSON) AsyncAPI file.
4. Run AsyncAPI: Preview Document from the Command Palette (⇧⌘P / Ctrl+Shift+P).

B) Locally in a browser (dev/test)

1. Install dependencies & build:

npm install
npm run build

2. Add a dev script to package.json to launch a web host:

{
  "scripts": {
    "open-in-browser": "vscode-test-web --extensionDevelopmentPath=. --port=8082 ."
  },
  "devDependencies": {
    "@vscode/test-web": "^1.x.x"
  }
}

Then:

npm run open-in-browser

This opens a web VS Code at http://localhost:8082. Open a workspace/folder that contains your AsyncAPI YAMLs, then run AsyncAPI: Preview Document.

Tip: If you don’t see the preview, ensure your file’s language mode is YAML (bottom-right of the status bar), and check Developer: Show Running Extensions to confirm activation.

Technical Changes

• Removed Node-only modules (e.g., direct path/fs usage).
• Introduced a lightweight pathUtils.ts for browser-safe path handling.
• Updated VS Code engine/types to enable web extension support.
• Removed unmaintained or web-incompatible pieces (e.g., legacy visualizer & Node-specific deps) to simplify the runtime and reduce bundle size.

Current limitations

• The web host cannot use Node APIs; all file access must go through vscode.workspace.fs.
• Auto-reload works on the active document save; changes to externally referenced files may not hot-reload yet.
• vscode.dev can’t read your local disk—open files from a GitHub repo or use File → Open File… (upload) for one-off files.

Automatic hot-reloading

Automatic hot-reloading on editor save, but currently, it doesn't reload when saving referenced external files.

Content Assistance

Available snippets:

Open an empty or otherwise yaml file and start typing one of the following prefixes, you may need to press Ctrl+space to trigger autocompletion in some cases:

• add asyncapi skeleton: Adds an asyncapi skeleton for jump starting your API editing.
• add asyncapi subscribe to async request: Inserts a new subscribe operation, for listening to incoming async requests/commands.
• add asyncapi publish event operation: Inserts a new publish operation, for producing domain events.
• add asyncapi message: Inserts a new message, you can choose it to be either a Request or an Event.

Once snippets are inserted use the <TAB> key to travel between snippet placeholders.

Paste as Schema

You can also autogenerate an Schema object from a JSON example.

Right-click inside #/components/schemas section and choose AsyncAPI: Paste as Schema from the context menu.

Credits

AsyncAPI Viewer utilizes the following open source projects:

• @asyncapi/asyncapi-react

Contributors

Ivan Garcia Sainz-Aja ivangsa Ruchi Pakhle Ruchip16