5 min readUpdated Aug 6, 2026Beginner
System Prompts
Learn about System Prompts in this comprehensive lesson.
A system prompt is a set of instructions given to Claude before the conversation starts — it shapes how Claude behaves throughout the chat (tone, role, rules, constraints).
On claude.ai, this is available through 'Custom Instructions' / 'Project instructions'. On the API/Console, developers pass a system prompt directly in code.
- Example: 'You are a friendly customer support agent for a shoe brand. Keep answers short and polite.'
- System prompts are great for keeping Claude consistent across many conversations