What is…

System prompt

Behind-the-scenes instructions that set a model's role, rules and style for the whole conversation.

Apps put a system prompt in front of every chat to define behavior: "You are a support agent for Acme. Be concise. Never discuss pricing." You control your own version through features like ChatGPT's custom instructions and Projects, Claude's Projects and styles, and Gemini's Gems.

Put stable preferences (your role, tone, formatting you like) in these settings so you stop repeating yourself.

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Which of these describes System prompt?

Related terms

Prompt

The instructions and context you give a model — the single biggest lever on the quality you get back.

Context engineering

Deliberately choosing what goes into the model's context — instructions, files, examples, tools — to get reliable results.

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