Extensions Capabilities Overview

Visual Studio Code offers many ways for extensions to extend its capabilities. It can sometimes be hard to find the right Contribution Points and VS Code API to use. This topic splits extension capabilities into a few categories. Each category describes:

  • Some functionalities your extension could use
  • Links to more detailed topics for using these functionalities
  • A few extension ideas

However, we also impose restrictions upon extensions to ensure the stability and performance of VS Code. For example, extensions cannot access the DOM of VS Code UI.

Common Capabilities

Common Capabilities are core pieces of functionality that you can use in any extension.

Some of these capabilities include:

  • Registering commands, configurations, keybindings, or context menu items.
  • Storing workspace or global data.
  • Displaying notification messages.
  • Using Quick Pick to collect user input.
  • Open the system file picker to let users select files or folders.
  • Use the Progress API to indicate long-running operations.

Theming

Theming controls the look of VS Code, both the colors of source code in the editor and the colors of the VS Code UI. If you've ever wanted to make it look like you're coding the Matrix by making VS Code different shades of green, or just wanted to create the ultimate, minimalist grayscale workspace, then themes are for you.

Extension Ideas

  • Change colors of your source code.
  • Change colors of the VS Code UI.
  • Port an existing TextMate theme to VS Code.
  • Add custom file icons.

Declarative Language Features

Declarative Language Features adds basic text editing support for a programming language such as bracket matching, auto-indentation and syntax highlighting. This is done declaratively, without writing any code. For more advanced language features, like IntelliSense or debugging, see Programmatic Language Features.

Extension Ideas

  • Bundle common JavaScript snippets into an extension.
  • Tell VS Code about a new programming language.
  • Add or replace the grammar for a programming language.
  • Extend an existing grammar with grammar injections.
  • Port an existing TextMate grammar to VS Code.

Programmatic Language Features

Programmatic Language Features add rich programming language support such as Hovers, Go to Definition, diagnostic errors, IntelliSense and CodeLens. These language features are exposed through the vscode.languages.* API. An extension can either use these API directly, or write a Language Server and adapt it to VS Code using the VS Code Language Server library.

Although we provide a listing of language features and their intended usage, nothing prevents you from using these API creatively. For example, CodeLens and Hovers are a great way to present additional information inline, while diagnostic errors can be used to highlight spelling or code style errors.

Extension Ideas

  • Add hovers that show sample usage of an API.
  • Report spelling or linter errors in source code using diagnostics.
  • Register a new code formatter for HTML.
  • Provide rich, context-aware IntelliSense.
  • Add folding, breadcrumbs and outline support for a language.

Workbench Extensions

Workbench Extensions extend the VS Code Workbench UI. Add new right-click actions to the File Explorer, or even build a custom explorer using VS Code's TreeView API. And if your extension needs a fully customized user interface, use the Webview API to build your own document preview or UI using standard HTML, CSS, and JavaScript.

Extension Ideas

  • Add custom context menu actions to the File Explorer.
  • Create a new, interactive TreeView in the Side Bar.
  • Define a new Activity Bar view.
  • Show new information in the Status Bar.
  • Render custom content using the WebView API.
  • Contribute Source Control providers.

Debugging

You can take advantage of VS Code's Debugging functionality by writing Debugger Extensions that connect VS Code's debugging UI to a specific debugger or runtime.

Extension Ideas

  • Connect VS Code's debugging UI to a debugger or runtime by contributing a Debug Adapter implementation.
  • Specify the languages supported by a debugger extension.
  • Provide rich IntelliSense and hover information for the debug configuration attributes used by the debugger.
  • Provide debug configuration snippets.

On the other hand, VS Code also offers a set of Debug Extension API, with which you can implement debug-related functionality on top of any VS Code debugger, in order to automate users' debugging experience.

Extension Ideas

  • Start debug sessions based on dynamically created debug configurations.
  • Track the lifecycle of debug sessions.
  • Create and manage breakpoints programmatically.

Restrictions

There are certain restrictions we impose upon extensions. Here are the restrictions and their purposes.

No DOM Access

Extensions have no access to the DOM of VS Code UI. You cannot write an extension that applies custom CSS to VS Code or adds an HTML element to VS Code UI.

At VS Code, we're continually trying to optimize use of the underlying web technologies to deliver an always available, highly responsive editor and we will continue to tune our use of the DOM as these technologies and our product evolve. To ensure that extensions cannot interfere with the stability and performance of VS Code, and that we can continue to improve the DOM of VS Code without breaking existing extensions, we run extensions in an Extension Host process and prevent direct access to the DOM.