Custom Instructions are the most underused feature in ChatGPT. They let you tell ChatGPT about yourself and your preferences once, and it applies to every conversation automatically. Instead of repeating "I'm a product manager who prefers concise answers in bullet points" in every chat, you set it once and forget it. Here's exactly what to write.

Where Do You Find Custom Instructions?

Settings → Personalization → Custom Instructions. You'll see two text boxes: "What would you like ChatGPT to know about you?" and "How would you like ChatGPT to respond?" Both have a 1,500 character limit. Use every character — this is the highest-leverage writing you'll do.

Key Takeaway

Custom Instructions are the difference between "generic AI assistant" and "my personalized AI assistant." Spend 10 minutes setting them up once, benefit in every conversation forever.

What Should You Put in "About You"?

Your role, your industry, your tools, your knowledge level, and what you typically use ChatGPT for. Be specific:

I'm a product manager at a B2B SaaS company (200 employees, Series B). I work primarily with engineering and design teams. Our stack: React, Node.js, PostgreSQL, hosted on AWS. I use Jira for project management, Figma for design, and Notion for documentation. I have intermediate SQL skills and basic Python. I use ChatGPT mainly for: writing PRDs, analyzing user research data, drafting stakeholder communications, and debugging SQL queries.

What Should You Put in "Response Style"?

Be concise. Default to bullet points for lists. When I ask for code, include comments explaining non-obvious logic. Don't add disclaimers like "As an AI..." — I know you're AI. When I share a problem, give me a solution first, then explain why it works. If I ask for a document (PRD, email, report), format it as if I'll send it directly — no placeholder text. Use specific numbers and examples over vague generalities. If you don't know something, say so instead of making something up.
Pro tip

Revisit your Custom Instructions every month. As your role evolves, your AI should evolve with it. Add new tools you've adopted, new types of tasks you do, or new output preferences you've developed.

Do this now: Open Settings → Personalization → Custom Instructions. Spend 10 minutes writing both sections. Be specific about who you are and how you want responses. Then start a new conversation and notice the difference immediately.