Basics

Custom instructions

Set persistent context so you stop repeating yourself.

Knowledge cards
Knowledge card
Fill Both Boxes: Who You Are and How to Answer
A guide to the two custom-instruction fields: the first tells ChatGPT who you are and what you're doing; the second tells it how you want answers shaped. Both apply to every new chat automatically.
L1 · Basic prompts
Comparison
Custom Instructions vs Memory vs Projects: What Goes Where
A routing guide for the three places ChatGPT stores context: global preferences go in custom instructions, project-specific rules and files go in a Project, and durable facts it learns go in Memory — with one-off detail staying in the prompt.
L2 · Context engineering
Best practice
Set Custom Instructions Once, Stop Repeating Yourself
Custom instructions are two standing fields — who you are and how you want answers — that ChatGPT applies to every new chat automatically.
L1 · Basic prompts
Best practice
Tune Custom Instructions From Answers You Didn't Like
A maintenance habit: treat every correction you find yourself repeating ('shorter', 'no bullet points', 'British spelling') as a signal to add a permanent custom instruction, so you fix it once instead of every chat.
L2 · Context engineering
ChatGPT custom instructions

Stop repeating your context

Custom instructions are a small settings panel where you tell ChatGPT, once, who you are and how you want it to respond. Anything you put there is applied to every new chat, so you stop re-typing your role, your preferences, and your formatting rules. It is the closest thing ChatGPT has to a persistent system prompt, and it is the single highest-return five minutes a regular user can spend. Well-written instructions make every future conversation start already tuned to you.

What to actually put in them

The useful fields are concrete: your role and domain ('product designer, mostly B2B SaaS'), how you want answers ('concise, no preamble, examples over theory'), and any standing constraints ('British English, assume no backend knowledge'). Avoid vague aspirations — 'be helpful' does nothing. Keep it short and specific, and revise it as you notice yourself correcting ChatGPT the same way repeatedly. Those repeated corrections are exactly what belongs in your instructions.

Frequently asked
What are ChatGPT custom instructions?

A settings panel where you tell ChatGPT who you are and how to respond, applied automatically to every new chat. They act like a persistent system prompt so you stop repeating your context.

What should I put in custom instructions?

Your role and domain, how you want answers formatted, and any standing constraints like language or assumed knowledge. Keep it short and specific — concrete preferences work, vague ones do not.

Do custom instructions apply to every chat?

Yes. Once set, they are applied to every new conversation until you change them, which is what makes them worth investing a few minutes to get right.