What are custom instructions in ChatGPT and how do I set them?

Custom instructions let you tell ChatGPT once about yourself and how you like answers, so you do not have to repeat it in every conversation. ChatGPT then applies these preferences to all your chats.

You will find them in ChatGPT's settings under the Personalization section. There are usually two parts: information about you, such as your work, interests and background, and how you want ChatGPT to respond, such as tone, length and format. Some versions also offer preset personality styles you can choose from.

Here is an example for a small business owner:

About me: "I run a digital marketing agency in Lucknow with eight employees. Our clients are mostly local schools, clinics and retailers. I use ChatGPT for client proposals, social media content and team emails."

How to respond: "Use simple, clear English suitable for Indian business readers. Keep answers concise unless I ask for detail. Use bullet points for lists. When writing marketing content, avoid exaggerated claims and clichés. Use rupees for prices. If something is uncertain, say so."

And one for a student:

About me: "I am a second-year B.Com student preparing for CA Foundation. My English is good, but complex topics are easier for me in Hindi."

How to respond: "Explain concepts step by step with simple examples. If a topic is complicated, add a short Hindi explanation. When I ask for practice questions, give answers separately at the end."

Good custom instructions share a few qualities:

1. They are specific. "Be helpful" adds nothing; "keep emails under 150 words" changes the output.
2. They explain your context, which helps ChatGPT choose suitable examples and vocabulary.
3. They focus on preferences you want every time, not one-off requests.
4. They avoid contradictions, like asking for "very detailed" and "very short" at once.

Custom instructions are different from memory. Instructions are written and controlled by you directly. Memory is information ChatGPT picks up and saves from conversations. Both shape your answers, and both can be edited or switched off.

If ChatGPT starts behaving oddly, check your custom instructions first. An old instruction, such as "always reply in Hindi," can cause unexpected results months later. Review them every few months and update them as your work or needs change.