What is a system prompt?
A system prompt is a set of instructions given to an AI model before the conversation starts, setting its role, rules and style for every reply. Users usually don't see it, but it shapes how the assistant behaves, for example staying polite, short, or on one topic.
How does a system prompt work?
Apps send the system prompt along with every user message. The model treats it as standing instructions, so the same model can act as a tutor in one app and a coding helper in another.
Why does a system prompt matter?
System prompts are how products customise a general model. Knowing they exist helps you understand why the same AI behaves differently in different apps.
An example
Example: A bank's chatbot has a system prompt saying 'Only answer questions about this bank's products, and never ask for an OTP.'
Related terms
Learn it properly
A system prompt is covered in Use AI Well, with short lessons, practice questions and instant feedback.