Customize GitHub Copilot Chat responses

  • 6 minutes

GitHub Copilot Chat can generate responses and code that match your coding practices and project requirements when given the right context. Instead of repeatedly adding this information in every chat prompt, you can store this context in files and automatically include it in every chat request.

There are three main ways to customize AI responses in Visual Studio Code:

  • Custom instructions: Define common guidelines for tasks like generating code, performing code reviews, or generating commit messages. These describe how tasks should be performed and can specify coding practices, preferred technologies, security rules, or commit message formats.

  • Prompt files: Define reusable prompts for common tasks. These standalone prompts describe what should be done and can include scaffolding components, performing code reviews, creating step-by-step guides, or generating implementation plans.

  • Custom chat modes: Define how chat operates, which tools it can use, and how it interacts with the codebase. Examples include planning modes with read-only access, research modes that access external resources, or role-specific modes like front-end development.

Custom instructions

Custom instructions enable you to describe guidelines that get responses matching your specific coding practices and tech stack. Instead of manually including this context in every chat query, custom instructions automatically incorporate this information with every chat request.

Note

Custom instructions are not taken into account for code completions.

Types of custom instructions

Visual Studio Code supports three ways to define custom instructions:

Type Description Use Cases
.github/copilot-instructions.md Single Markdown file in workspace, automatically included in all requests, cross-editor support. General coding practices, preferred technologies, project-wide requirements.
.instructions.md files Multiple Markdown files with glob pattern support, workspace or user profile storage. Task-specific instructions, granular control over when instructions apply.
Visual Studio Code settings Instructions in user/workspace settings for specific scenarios. Code generation, test generation, commit messages, code reviews, PR descriptions.

You can combine these approaches, but avoid conflicting instructions as no priority order is applied.

Custom instructions examples

General coding guidelines:

---
applyTo: "**"
---
# Project coding standards

## Naming Conventions
- Use PascalCase for component names, interfaces, and type aliases.
- Use camelCase for variables, functions, and methods.
- Prefix private class members with underscore (_).
- Use ALL_CAPS for constants.

## Error Handling
- Use try/catch blocks for async operations.
- Implement proper error boundaries in React components.
- Always log errors with contextual information.

TypeScript and React guidelines:

---
applyTo: "**/*.ts,**/*.tsx"
---
# TypeScript and React standards

Apply the [general coding guidelines](./general-coding.instructions.md) to all code.

## TypeScript Guidelines
- Use TypeScript for all new code.
- Follow functional programming principles where possible.
- Use interfaces for data structures and type definitions.
- Prefer immutable data (const, readonly).
- Use optional chaining (?.) and nullish coalescing (??) operators.

## React Guidelines
- Use functional components with hooks.
- Follow the React hooks rules (no conditional hooks).
- Use React.FC type for components with children.
- Keep components small and focused.
- Use CSS modules for component styling.

Use .github/copilot-instructions.md file

Store custom instructions in a .github/copilot-instructions.md file at your workspace root to describe coding practices, preferred technologies, and project requirements. These instructions apply only to the workspace and are automatically included in every chat request.

Setup steps:

  1. Set github.copilot.chat.codeGeneration.useInstructionFiles to true.
  2. Create .github/copilot-instructions.md at workspace root.
  3. Describe instructions using natural language and Markdown format.

Note

This file works across Visual Studio Code, Visual Studio, and GitHub.com.

Use .instructions.md files

Create multiple .instructions.md files for specific tasks, programming languages, frameworks, or project types. These can be automatically applied based on file patterns or manually attached to chat prompts.

File locations:

  • Workspace files: Stored in .github/instructions folder, available only within the workspace.
  • User files: Stored in Visual Studio Code profile, available across multiple workspaces and synced via Settings Sync.

File structure:

---
description: "Brief description of the instructions file"
applyTo: "**/*.ts,**/*.tsx"  # Glob pattern for automatic application
---
# Instructions content in Markdown format

Create and use instructions files:

  1. Run Chat: New Instructions File from Command Palette.
  2. Choose workspace or user location.
  3. Enter name and author instructions in Markdown.
  4. Use Chat: Configure Instructions to edit existing files.

Manual attachment:

  • In Chat view: Add Context > Instructions
  • Command Palette: Chat: Attach Instructions

Automatic application: Use applyTo metadata with glob patterns (** for all requests, specific patterns for targeted application)

Specify custom instructions in settings

Configure custom instructions in Visual Studio Code settings for specific scenarios:

Scenario Setting
Code generation github.copilot.chat.codeGeneration.instructions
Test generation github.copilot.chat.testGeneration.instructions
Code review github.copilot.chat.reviewSelection.instructions
Commit messages github.copilot.chat.commitMessageGeneration.instructions
PR titles/descriptions github.copilot.chat.pullRequestDescriptionGeneration.instructions

Define instructions as text or reference external files:

"github.copilot.chat.codeGeneration.instructions": [
  {
    "text": "Always add a comment: 'Generated by Copilot'."
  },
  {
    "text": "In TypeScript always use underscore for private field names."
  },
  {
    "file": "general.instructions.md"
  },
  {
    "file": "db.instructions.md"
  }
]

Best practices for custom instructions

  • Keep instructions concise: Each instruction should be a single, simple statement.
  • Avoid external references: Don't refer to external coding standards or resources.
  • Organize by topic: Split instructions into multiple files for better organization.
  • Enable team sharing: Store instructions in version-controlled files for team collaboration.
  • Use targeted application: Leverage applyTo property for file-specific instructions.
  • Reference efficiently: Reference custom instructions in prompt files to avoid duplication.

Summary

Custom instructions in GitHub Copilot Chat allow you to define coding practices, preferred technologies, and project requirements that are automatically included in every chat request. By using .github/copilot-instructions.md files, .instructions.md files, or Visual Studio Code settings, you can ensure that AI-generated responses align with your coding standards and project needs. This approach enhances the quality and relevance of AI assistance while maintaining control over the coding process.