System prompt
A system prompt is a persistent instruction that sets a model’s role, rules, and boundaries for an entire conversation, separate from the individual messages a user sends.
System prompts are weighted more heavily than user turns by most chat models and persist across every exchange, which makes them the right place for anything that should always be true: the persona, the tone, the refusal rules, the output format. Anything specific to one request belongs in the user message instead.
Related terms
- User message
- A user message is a single turn of input in a conversation with a language model, carrying the specific request and any material that request depends on.
- Role prompting
- Role prompting is telling a model to adopt a specific persona or professional perspective so that its vocabulary, priorities, and level of detail match that role.
- Assistant prefill
- An assistant prefill is text placed at the start of the model’s own reply so that it continues from there instead of choosing its own opening.
More on core concepts
See the full glossary, read the guides, or put it into practice in the prompt builder.