PromptivityWhat are ChatGPT custom instructions, and how do I set them up?
Custom instructions are standing notes that ChatGPT considers in every chat: who you are, what you use it for, and how you want answers. They are available on all plans, on the web, desktop, iPhone and Android, and you can change or remove them at any time.
Where to find them
On the web or desktop app, open Settings, select Personalization, make sure Enable customization is on, and type into the Custom Instructions field. On iPhone and Android, OpenAI's help page lists the same steps under Settings, then Customize ChatGPT. To switch them off later, turn Enable customization off. You can also delete the text.
What to put in them
Two kinds of information help most. First, a little about you: your work, what you mostly use ChatGPT for, and how much you already know about those topics. Second, how you want answers: length, format, tone, and whether it should ask a question when your request is unclear. A short example:
- I run a small bookkeeping business and use ChatGPT for client emails and checking my reasoning.
- Keep answers short. Use plain words and bullet points for steps.
- If my request is unclear, ask me one question before answering.
What to leave out
Leave out passwords and anything you wouldn't want stored, such as sensitive health or financial details. One-off project details are better in the chat itself. OpenAI's help page notes that information from custom instructions may be used to improve its models unless you opt out in Data controls.
How long they can be
Free and Go plans can save up to 1,500 characters of custom instructions. Plus, Pro, Business, Enterprise and Education plans can save up to 5,000. Shorter instructions are easier to check and adjust.
Custom instructions and memory
They are different. OpenAI's help page describes custom instructions as direct guidance you write, while memory picks up relevant details across conversations. If the two conflict, update the one that's out of date.
Check that they work
Ask the same real question twice: once in a normal chat and once in a temporary chat set to Unpersonalized, which doesn't use your memories or custom instructions. Compare the two answers. If you can't see a difference, make one instruction more specific and try again.
Sources
Checked against OpenAI's help pages on 17 October 2026: ChatGPT Custom Instructions, Memory in ChatGPT. ChatGPT changes often, so if your screen looks different, trust your screen.
Want the step-by-step version? ChatGPT Setup Workbook: Quick Start is a short PDF guide for $12.
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