How to write GitHub and Microsoft
Copilot system prompts

Understanding the two Copilot products

Copilot is two distinct products from Microsoft with different use cases, different system prompt approaches, and different audiences. GitHub Copilot is a developer tool for code completion and AI pair programming. Microsoft 365 Copilot is an AI assistant embedded in Word, Excel, Teams, and Outlook with deep Microsoft Graph integration.

GitHub Copilot - instructions via copilot-instructions.md

Create .github/copilot-instructions.md in your repository root. See the GitHub Copilot custom instructions documentation.

# Tech stack
- TypeScript, React 18, Next.js App Router
- Tailwind CSS v3, shadcn/ui components
- Prisma for database, PostgreSQL

# Code standards
- TypeScript strict mode always
- Server components unless client interactivity needed
- Co-locate tests with source files (.test.ts)

# Architecture
- API routes in app/api/ follow REST conventions
- Auth handled by NextAuth - do not reimplement

# Behavior
- Explain significant changes before making them
- Ask before adding new dependencies
- Write JSDoc for all exported functions

Microsoft 365 Copilot - system prompts via agents

Individual users can create custom Copilot agents via Copilot Studio. Each agent has its own system prompt (called "instructions"), access to specific data sources, and defined behavior.

Common questions

Do GitHub Copilot instructions work in GitHub.com and VS Code?

Yes. .github/copilot-instructions.md is recognized across all GitHub Copilot interfaces.

Can I have different instructions for different branches?

Not directly - .github/copilot-instructions.md applies at the repository level. For different instruction contexts, use the VS Code settings.json approach with multiple scoped files.

How does GitHub Copilot compare to Cursor?

Both support custom instructions via repository files. Cursor's .cursor/rules/ supports more granular scoping. GitHub Copilot integrates directly with GitHub workflows. See our Cursor guide for comparison.