What Is a System Prompt?
A system prompt is a hidden instruction that sets the AI's behavior for the entire conversation, not just one message.
How System Prompts Work
System prompts are processed before user messages, setting a persistent context that influences every response.
Effective System Prompts
- "You are a helpful coding assistant. Always provide working code examples."
- "You are a brutally honest business advisor. Don't sugarcoat feedback."
- "You are a patient tutor. Never give the answer directly — guide the student to discover it."
Platform Support
- ChatGPT: Custom Instructions feature
- Claude: System prompt in API calls
- Gemini: System instructions available in API
Best Practices
- Keep it concise
- Be specific about behavior, not personality
- Test across different types of requests
- Iterate based on actual outputs
Combine with Regular Prompts
System prompts set the stage. Regular prompts give the specific task. Use both for maximum control.