Custom instructions let you set your context and preferences once, so ChatGPT applies them to every new conversation — no more repeating yourself.
1. Open custom instructions
Click your profile (bottom-left) → Settings → Personalization → Custom instructions.
2. Fill in the two boxes
What would you like ChatGPT to know about you? Your role, stack, audience — anything that should color answers:
I'm a solo indie developer building small web apps with Astro and TypeScript.
I deploy on Cloudflare. Assume an intermediate level.
How would you like ChatGPT to respond? Tone, format, length:
Be concise and direct. Give the answer first, then a short why.
Use code blocks for commands. Skip disclaimers.
3. Save and test
Save, then start a new chat — existing chats don’t pick up the change. Ask something and watch it follow your preferences.
Tips
- Keep it short and specific; vague instructions get ignored.
- Put hard rules (“always X”, “never Y”) in the second box.
- For persistent project knowledge, use Claude Projects or a CLAUDE.md on the dev side.