Jargon:System prompt
1 min read
Say this at the party
“A system prompt is the hidden set of instructions an AI gets before you type anything. It sets its role, rules and tone.”
In plain English
When you chat with an AI, you are not the first to speak. Before your message, the app has already given it a block of instructions you usually can't see.
That is the system prompt. It might say "You are a friendly support agent for a bike shop", tell it today's date, or set rules like "never give medical advice".
Two apps built on the same AI can feel completely different, mostly because of their system prompts.
Where it came from
The term grew up with chat-style AI tools, which let developers send a separate "system" message that sits above everything the user types. Anthropic now publishes the system prompts it uses in the Claude apps, so anyone can read them.
See it in action
Ben asks a cooking website's chatbot to help with his maths homework. It politely steers him back to recipes, because its system prompt says to stick to cooking.
What people get wrong
- A system prompt isn't a lock. Clever wording can sometimes talk an AI out of it, which is what jailbreaks and prompt injection try to do.
- It doesn't change what the AI knows. It only shapes how it behaves in that conversation.
Go deeper
- GuideAnthropicSystem prompts - Claude Platform DocsRead the real system prompts Anthropic gives Claude in its own apps.
- GuideAnthropicPrompting best practices - Claude Platform DocsHow developers use a system prompt to give an AI a role, with examples.
- ArticleWikipediaPrompt engineering - WikipediaThe wider picture of how instructions shape what AI produces.
Related jargon
Drafted with AI. The AI Council (Claude, ChatGPT and Gemini) gave counsel. Phin signed it off.