Glossary
System prompt
A system prompt is the hidden instruction sheet an AI receives before your conversation starts. It sets the assistant's role, rules, and tone, which is why the same model can behave differently in different apps.
Before you type your first word, the AI has already read a briefing you never see: “You are a helpful assistant. Be concise. Refuse harmful requests. Today’s date is…” That briefing is the system prompt, and it shapes every answer that follows.
It’s like a new waiter’s first day. Before any customer walks in, the bar owner says: “Be friendly, suggest the daily special, never comment on prices, send complaints to me.” Customers only ever see the waiter, but the owner’s briefing decides how every table gets treated.
This explains a common surprise: the “same” model acting bubbly in one app and strict in another. Different system prompts. It also explains why companies building on an AI model guard their system prompts: that text is a big part of the product’s personality.
Where you’ll meet this
You won’t see most big platforms’ system prompts directly. Anthropic is the exception: it publishes the system prompts behind the claude.ai and mobile apps, model by model, in its documentation. And you get your own mini version: ChatGPT’s custom instructions, your Instructions for Gemini, and Instructions for Claude all inject your standing notes the same way. Our setup wizard helps you write them once and well.