AI Custom Instructions: Set Them Once, Get Better Results Forever

Every time you start a new conversation with ChatGPT or Claude, you're talking to an AI that knows nothing about you. Custom instructions fix this permanently. Set them once, and every future conversation starts with your context — your role, your industry, your writing preferences, your pet peeves. Here's how to set them up on every major platform and what to actually put in them.

ChatGPT Custom Instructions

Go to Settings → Personalization → Custom Instructions. You'll see two fields: "What would you like ChatGPT to know about you?" and "How would you like ChatGPT to respond?"

Field 1 — About You: "I'm a marketing director at a B2B SaaS company with 50 employees. I manage a team of 4. Our product is a project management tool for construction companies. I spend most of my day on email, content strategy, and campaign analysis. I use Google Workspace."

Field 2 — Response Style: "Use a direct, professional tone. Avoid corporate jargon. Keep responses concise — I prefer 3 short paragraphs over 10 bullet points. When I ask about marketing, assume B2B SaaS context. When showing examples, make them relevant to construction or project management. Don't start responses with 'Great question!' or 'Certainly!'"

Claude Custom Instructions

Claude has two levels. Global preferences (Settings → User Preferences) apply to every conversation. Project instructions apply to specific Projects — these are more powerful because they include uploaded documents.

Global preferences example: "I'm a freelance writer and content strategist. I work with AI tool companies and SaaS startups. My writing is conversational, direct, and skeptical of hype. I use contractions. I don't use 'leverage,' 'unlock,' 'delve,' or 'game-changer.' When I ask for drafts, write in first person. When I ask for analysis, be structured and specific."

Project instructions are covered in our Claude Projects guide — they're where the real power is.

Template Custom Instructions (Copy and Modify)

For knowledge workers: "I'm a [role] at a [company type/size]. My daily work involves [3 main tasks]. I prefer responses that are [tone preferences]. Keep answers under [length preference] unless I ask for more detail. When giving advice, assume I have [basic/intermediate/advanced] knowledge of the topic. Avoid [specific phrases or patterns you dislike]."

For business owners: "I run a [business type] with [size/revenue]. My customers are [description]. I'm the sole decision-maker for [areas]. When I ask for strategies, they need to be executable by a small team with limited budget. Be direct about what won't work, not just what will."

For students: "I'm studying [subject] at [level]. I learn best through examples and analogies. When explaining concepts, start simple and add complexity. Don't give me answers directly — walk me through the reasoning so I learn the process."

What NOT to Put in Custom Instructions

Don't include sensitive information like financial details, passwords, health conditions, or specific client information. Custom instructions persist across all conversations and may be processed by the AI provider.

Don't make them too long. Both ChatGPT and Claude have character limits, and overly detailed instructions can conflict with each other. Keep it to the 5-10 most important things about you and your preferences.

Don't include task-specific instructions. "Always write in haiku format" only makes sense if you always want haiku. Custom instructions should be universally applicable preferences, not per-task requirements.

For help refining the prompts you write within these customized environments, try our Prompt Optimizer.

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