Instructions · kept current

Where to paste custom instructions in Claude, ChatGPT, Grok and Duck.ai

Every major AI has one box that it reads before anything else — before its memory of you, before your question. This is where that box lives in each one.

Last checked 14 September 2026

Menus move. If yours doesn’t look like this, search your AI’s settings for instructions, preferences or saved info — the box is almost always one of those three words.

Which size goes where

Small (up to 500 characters) fits every app, even Duck.ai. Medium (up to 1,500) fits ChatGPT Free and up, and Claude. Large (about a page) fits ChatGPT Plus and up, and Claude. Every space and line break counts.

Claude

  1. Open Settings → Profile.
  2. Find the box labelled “What personal preferences should Claude consider in responses?”
  3. Paste your constitution in and save.

Claude reads it at the start of every conversation, including new ones.

ChatGPT

  1. Open Settings → Personalization → Custom instructions.
  2. Paste your constitution into the box that asks what ChatGPT should know about you — or the one about how it should respond. Either works; the first is the better fit.
  3. Save.

The Free and Go plans take up to 1,500 characters there, so use your Medium or your Small. Plus and up take 5,000, so your Large fits.

Grok

  1. Look for Customize Grok — in Settings, or on the button beside the message box.
  2. Paste your constitution into Custom instructions.
  3. Save.

Duck.ai (DuckDuckGo)

  1. Open a chat in Duck.ai, DuckDuckGo’s AI chat.
  2. At the bottom left of the chat window, tap Customize Responses: the second button in.
  3. Paste your constitution in and save.

Your Small fits here.

Gemini, Copilot, Perplexity and the rest

Most others have the same thing under a different name. Gemini calls it Saved info. Copilot and Perplexity each have a personalization or preferences screen in settings. Search the settings for instructions, preferences or saved info and paste it into whichever box takes free text about you.

What if there’s no box at all?

Paste your constitution as the first message of a new chat, before your actual question. Clunky — you’ll do it every time — but it works, and it works immediately. Your Small is short enough for this.

How to check it actually took

Start a brand new conversation — not the one you were already in — and ask it to tell you, in its own words, how you want to be answered. If it can describe your constitution back to you, it’s loaded. If it can’t, the paste didn’t save, or you’re in an old conversation that started before you saved it.

Worth knowing: the instructions box and the memory feature are two different things, and memory can quietly work against what you’ve written. Instructions are what you stated; memory is what the AI guessed. Getting the memory settings right is the other half of the job.

Don’t have one to paste yet?

Write one free, in about a minute. Three plain questions, nothing filled in for you.

Write yours — free

Last checked 14 September 2026 · Something wrong or out of date? Tell us