ChatGPT System Prompt: What It Is and Where to Set It

A system prompt is the standing instruction an AI reads before your messages: its role, rules and style. In the ChatGPT app, you set one through custom instructions, a Project or a custom GPT; developers set it in the API. A template and three examples are below.

Blueprint sketch of an instruction card above a stack of chat bubbles, linked by flowing lines

What a system prompt does

Your normal messages ask for one thing. A system prompt sets the ground rules for the whole chat: who the AI should act as, what it must always or never do, and how answers should look. It's why the same model can feel like a tutor in one app and a coding helper in another.

Where to set it, app by app

ChatGPT (app): use Settings → Personalization → Custom instructions for every chat. For one topic, put instructions in a Project (if your plan has them). A custom GPT has its own instructions box.

Claude (app): open a Project and use Set project instructions.

Gemini (app): create a Gem and write its instructions.

Developers (API): OpenAI, Anthropic and Google each let you pass a system-level instruction with the request. Check each provider's API docs for the exact field name.

A system prompt template

Role: You are a [role] helping [who] with [goal].
Always: Lead with the answer. Ask one question if my request is unclear. Say when you're unsure.
Never: Invent facts, links or quotes. Pad answers with filler.
Format: [bullets / short paragraphs / code first]. Keep answers under [N] words unless I ask for more.

3 ready-to-edit examples

Editor

Role: You are a blunt copy editor.
Always: Show edits as before/after pairs and explain each in one line.
Never: Change my meaning or add new claims.

Weekly planner

Role: You are my planning assistant.
Always: Sort tasks into Today / This week / Later. Flag anything with a deadline.
Never: Schedule more than 3 big tasks per day.

Study coach (adults)

Role: You are a study coach for an adult learner.
Always: Ask what I think first. Explain only after I've tried. End with a 3-question quiz.
Never: Give me the answer before I've tried.

Tips that make it stick

Keep it short. A few clear rules hold better than a page of them.
Avoid contradictions, like "be brief" plus "explain everything."
Test it. Ask three typical questions and adjust the rules that didn't hold.
Start a new chat after changing it.

System prompt vs. custom instructions vs. persona

Custom instructions are ChatGPT's built-in way to set a system-style prompt for every chat. A system prompt is the general term. A persona is a full system prompt with a job: a profile it builds with you, routines and check-ins.

More: 12 custom instructions examples and how to make ChatGPT less of a yes-man.

FAQ

Can I see ChatGPT's own system prompt? OpenAI doesn't show it in the app. Focus on the instructions you control. Does a system prompt guarantee behavior? No. It steers the AI, but it can still slip. Check anything important. Can I reuse one prompt across apps? Yes. Paste the same text into ChatGPT, a Claude Project or a Gemini Gem, then test it.

A free LOADOUT persona is a system prompt with a job: BOB runs your week and ALICE plans like a chief of staff. Paste one into the AI you already use. See the personas →

Free LOADOUT personas are for adults 18+. They run on your own AI account (for example ChatGPT, Claude or Gemini), so follow your AI provider's terms; we don't see your chats. AI can be wrong; check anything important.