ChatGPT System Prompt Generator

Build Custom GPT Instructions • Persona, Purpose & Strict Rules

Note on availability: as of February 2026, creating and publishing a new Custom GPT is not available on personal ChatGPT accounts (Free, Go, Plus, Pro) — only in Business, Enterprise, or Edu workspaces, or when editing a GPT you already created. The text this tool generates still works in every one of those places, and equally well as a system prompt for the OpenAI API or the simpler personal "Custom Instructions" setting — it's just plain text for whichever field you're filling in.
Quick Start Templates

Start from a common assistant type, then adjust anything below.

Name & Description
Instructions
Tone, communication style, character traits — this shapes how every response feels.
What this assistant is for, and what topics it covers.
One rule per line. OpenAI's own guidance: prefer positive, concrete instructions ("Always do X") over long lists of prohibitions where possible — though hard boundaries are fine as "Never" rules.
Optional — length, structure, or formatting preferences.
Optional — what it should do when asked about something outside its purpose.
Conversation Starters Optional
Example prompts shown to users when they open the GPT.
About
Where This Goes
Contact

About the System Prompt Generator

This tool assembles a structured "Instructions" block for a Custom GPT — the text that defines its persona, purpose, strict behavioral rules, response format, and how it should handle out-of-scope requests. The output follows OpenAI's own documented guidance for writing GPT instructions: clear headings and lists rather than dense paragraphs, and positive, concrete rules where possible. Persona and Purpose are the two fields that most shape how a GPT behaves, so they're the only two treated as effectively required — everything else adds precision on top. All generation happens locally in your browser; nothing you type is ever uploaded anywhere.