System Prompt
A privileged instruction block sent before the conversation that sets the model's persona and rules.
Full Definition
The system prompt is a special message — separated from the user conversation — that establishes the model's identity, behavioural guidelines, knowledge constraints, tone, and any application-specific rules. It is processed before user messages and typically carries higher weight in the model's attention. System prompts are the primary mechanism by which developers customise a general-purpose model for a specific product: a customer service bot, a coding assistant, or a creative writing tool. They can range from one sentence to thousands of tokens. Because system prompts often contain proprietary instructions, protecting them from prompt injection and extraction is a key security concern.
Examples
'You are Aria, a helpful assistant for AcmeCorp. Always respond in English. Never discuss competitor products. If asked about pricing, direct users to /pricing.'
A multi-paragraph system prompt for a medical information tool that defines the assistant's role, disclaimers, citation requirements, and out-of-scope topics.
Apply this in your prompts
PromptITIN automatically uses techniques like System Prompt to build better prompts for you.