VS Code Extensions Programming Cheat Sheet

Updated 2026-04-29

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Visual Studio Code extensions are plug-ins that enhance the editor's functionality through a rich JavaScript/TypeScript API. Extensions can add commands, UI components, language features, debugging support, AI-powered chat participants, and custom editors — essentially anything that customizes or extends the editing experience. The extension API is comprehensive and well-structured, allowing developers to build everything from simple commands to complex language servers and MCP-integrated AI tools, with contributions declared in package.json and runtime behavior implemented through activation events and the vscode namespace. Understanding the lifecycle (activation, execution, deactivation) and contribution model is key to building efficient, well-integrated extensions.

What This Cheat Sheet Covers

This topic spans 29 focused tables and 221 indexed concepts, 152 flashcards. Below is a complete table-by-table outline of this topic, spanning foundational concepts through advanced details.

Table 1: Extension Manifest ConfigurationTable 2: Activation EventsTable 3: Contribution PointsTable 4: Core API NamespacesTable 5: Extension Lifecycle and Resource ManagementTable 6: Text Editor and Document OperationsTable 7: UI ComponentsTable 8: Views and Tree ViewsTable 9: Language FeaturesTable 10: Diagnostics and DecorationsTable 11: Workspace and FilesTable 12: Configuration and StorageTable 13: WebviewsTable 14: Custom EditorsTable 15: Notebook APITable 16: AI / Language Model APITable 17: Source Control (SCM) APITable 18: Testing APITable 19: DebuggingTable 20: Authentication APITable 21: When Clauses and Context KeysTable 22: Semantic Highlighting and TokensTable 23: Language Server Protocol (LSP)Table 24: Language ConfigurationTable 25: TasksTable 26: Publishing and PackagingTable 27: MCP Server IntegrationTable 28: Bundling and ToolingTable 29: Localization (l10n)

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Table 1: Extension Manifest Configuration

The package.json manifest is the first file VS Code reads, and every extension begins here. These fields declare the identity that forms your publisher.name ID, the entry point that gets loaded, the engine version that gates which APIs you can call, and the marketplace metadata that decides how discoverable you are. Getting the required ones right — name, publisher, version, engines, main — is the difference between an extension that installs and one that's rejected.

Field	Example	Description
name	`"name": "my-extension"`	• Unique identifier for the extension • must be lowercase alphanumeric with hyphens • used in extension ID as `publisher.name`.
displayName	`"displayName": "My Extension"`	• Human-readable name shown in marketplace and Extensions view • can contain spaces and capitals.
publisher	`"publisher": "mycompany"`	• Publisher identifier • must match your VS Code Marketplace publisher account • forms the full extension ID.
version	`"version": "1.0.0"`	• Semantic version in `major.minor.patch` format • required for publishing and updates.
engines.vscode	`"engines": { "vscode": "^1.85.0" }`	• Minimum VS Code version required • uses semantic versioning range syntax • determines API availability.
main	`"main": "./out/extension.js"`	• Entry point file path for extension activation • exports `activate()` and `deactivate()` functions.
activationEvents	`"activationEvents": ["onCommand:ext.hello"]`	• Array of events triggering extension loading • *use specific events instead of `` for better performance**.
contributes	`"contributes": { "commands": [...] }`	• Declares UI contributions (commands, menus, views, etc.) • defines what the extension adds to VS Code.
categories	`"categories": ["Programming Languages"]`	• Marketplace categories for discovery • use predefined values like `Formatters`, `Linters`, `Debuggers`.
keywords	`"keywords": ["python", "linter"]`	• Search terms for marketplace • improves discoverability • maximum 5 recommended.
icon	`"icon": "images/logo.png"`	• Relative path to the extension icon (128×128 PNG) • displayed in marketplace and Extensions view.
repository	`"repository": { "type": "git", "url": "https://github.com/..." }`	• Source code repository URL • enables "Repository" link in marketplace.
l10n	`"l10n": "./l10n"`	• Path to folder containing `bundle.l10n.{locale}.json` translation files • required for multi-language extension support.

Table 2: Activation Events

Extensions stay dormant until something wakes them, and activation events are the triggers that decide when. The whole point is laziness for performance — you want your code to load only when a relevant command runs, a matching language opens, or a custom view appears, not on every startup. That's why the * event at the bottom comes with a blunt warning: it loads on launch and drags down everyone's editor.

Event	Example	Description
onCommand	`"onCommand:extension.doSomething"`	• Activates when specific command is invoked • most common activation pattern.

The rest of this section is part of the full cheat sheet

Table 3: Contribution Points

Contribution points are the declarative half of an extension — the things you register in package.json so VS Code knows about them before any code runs. This is a long list because it's essentially the menu of everything you can add to the editor: commands, menus, keybindings, settings, views, themes, snippets, debuggers, custom editors, notebooks, and the newer AI surfaces like chat participants and MCP providers. Skim it as a catalog of what's possible, then pair each entry with its runtime counterpart in the API tables that follow.

Contribution	Example	Description
commands	`"commands": [{ "command": "ext.hello", "title": "Hello" }]`	• Registers commands available via Command Palette or keybindings • requires activation event.

The rest of this section is part of the full cheat sheet

Table 4: Core API Namespaces

The entire vscode API is organized into a handful of top-level namespaces, and learning which one owns which capability is the fastest way to find what you need. window handles UI, workspace handles files and configuration, commands runs and registers actions, languages powers IntelliSense-style features — and newer namespaces like lm and chat open the door to AI. Think of this as the map; the later tables zoom into individual namespaces.

Namespace	Example	Description
vscode.commands	`vscode.commands.registerCommand('id', callback)` `vscode.commands.executeCommand('workbench.action.files.save')`	• Registers and executes commands • executeCommand can invoke built-in or extension commands.

The rest of this section is part of the full cheat sheet

Table 1: Extension Manifest Configuration

Field	Example	Description
name	`"name": "my-extension"`	• Unique identifier for the extension • must be lowercase alphanumeric with hyphens • used in extension ID as `publisher.name`.
displayName	`"displayName": "My Extension"`	• Human-readable name shown in marketplace and Extensions view • can contain spaces and capitals.
publisher	`"publisher": "mycompany"`	• Publisher identifier • must match your VS Code Marketplace publisher account • forms the full extension ID.
version	`"version": "1.0.0"`	• Semantic version in `major.minor.patch` format • required for publishing and updates.
engines.vscode	`"engines": { "vscode": "^1.85.0" }`	• Minimum VS Code version required • uses semantic versioning range syntax • determines API availability.
main	`"main": "./out/extension.js"`	• Entry point file path for extension activation • exports `activate()` and `deactivate()` functions.
activationEvents	`"activationEvents": ["onCommand:ext.hello"]`	• Array of events triggering extension loading • *use specific events instead of `` for better performance**.
contributes	`"contributes": { "commands": [...] }`	• Declares UI contributions (commands, menus, views, etc.) • defines what the extension adds to VS Code.
categories	`"categories": ["Programming Languages"]`	• Marketplace categories for discovery • use predefined values like `Formatters`, `Linters`, `Debuggers`.
keywords	`"keywords": ["python", "linter"]`	• Search terms for marketplace • improves discoverability • maximum 5 recommended.
icon	`"icon": "images/logo.png"`	• Relative path to the extension icon (128×128 PNG) • displayed in marketplace and Extensions view.
repository	`"repository": { "type": "git", "url": "https://github.com/..." }`	• Source code repository URL • enables "Repository" link in marketplace.
l10n	`"l10n": "./l10n"`	• Path to folder containing `bundle.l10n.{locale}.json` translation files • required for multi-language extension support.

Table 2: Activation Events

Event	Example	Description
onCommand	`"onCommand:extension.doSomething"`	• Activates when specific command is invoked • most common activation pattern.

Table 3: Contribution Points

Contribution	Example	Description
commands	`"commands": [{ "command": "ext.hello", "title": "Hello" }]`	• Registers commands available via Command Palette or keybindings • requires activation event.

Table 4: Core API Namespaces

Namespace	Example	Description
vscode.commands	`vscode.commands.registerCommand('id', callback)` `vscode.commands.executeCommand('workbench.action.files.save')`	• Registers and executes commands • executeCommand can invoke built-in or extension commands.