AI glossary
System prompt
A system prompt is the standing instruction sent before the conversation that sets a model's role, tone and rules for every reply in a chat.
Chat APIs take messages with roles: system, user and assistant. The system message is written by the developer, not the user, and it stays at the top while the conversation grows below it.
A support bot might say: you answer questions about our booking system, you reply in two or three sentences, and you say so when you do not know. Every user message is then read in that light.
It is guidance, not a lock. A determined user can talk a model out of its system prompt, so anything that must never happen is enforced in code, not only asked for in words.
Learn it hands-on
These free lessons teach it with commands to run in a lab and checked tasks. Read them whole with no account.