To set your custom instructions in Claude, click your initials in the bottom-left corner, open Settings, and find Instructions for Claude. Paste a short note on who you are, how you want it to write, and what to avoid, then save. It applies to every new chat from then on.
Why this is worth two minutes
Claude starts every conversation with a blank memory of you, so unless you say otherwise it guesses your job, your reader and your style, and it guesses the same average way every time. That guess is why the answers can feel a bit generic. The instructions box fixes it at the source: you write down the handful of things that change how it should reply, it keeps them in the background, and every future chat starts already knowing them. You do the explaining once instead of at the top of every conversation.
What to paste
Keep it short and plain. These are the five things that actually change how Claude answers you. Fill in the brackets and delete anything that does not apply.
Who I am and what I do: [one line about you and your work, for example: I run a small skincare brand and write my own emails and posts.] How to write to me: short sentences, plain words, UK English, no jargon. Get to the point. Tone: [pick one, for example warm and direct.] Never do this: no em dashes, no exclamation marks, no corporate filler (delve, leverage, seamless, "in today's fast-paced world"), and no tacked-on summary at the end. When you are not sure: ask me one question before you assume, and do not make anything up.
That banned-words habit is borrowed from a real practitioner, Jess Allison, who keeps a blacklist in her own instructions. If you want the full list of phrases that give AI writing away, we keep one in the AI writing tells guide.
Where to put it
- Open your settings. Click your initials in the bottom-left corner of Claude, then open Settings.
- Find Instructions for Claude. Look for the section called Instructions for Claude. The label has been renamed before, so if you do not see those exact words, look for the personalisation or instructions option under Settings.
- Paste and fill it in. Drop the template into the box and swap in your own details.
- Save, then check it took. Open a brand new chat and ask it anything. It should reply in the style you set. It only kicks in on new chats, so a conversation you already had open will not pick it up.
On ChatGPT
The same thing exists in ChatGPT, called custom instructions, in its settings. The note you wrote works there too, so you can paste the same one across both. Only the place you put it changes.
The honest bit
- Keep it short. A long wall of rules pulls Claude in too many directions and can make answers worse, so stick to the few that matter.
- This sets your default voice across every chat. For one body of work that needs its own rules, use the instructions box inside a Claude Project, which needs a paid plan.
- It nudges rather than forces, so Claude will still slip sometimes. Read what it writes and correct it in the chat when it drifts.
A few quick questions
Doesn't Claude have a memory now? Do I still need this?
Yes it has a memory, and yes you still want this. Claude's memory picks things up from your chats over time and weighs them for relevance (Claude's own explainer). The instructions box is a different thing: it is the fixed set of rules you choose, applied on every new chat. Put your standing rules in the box, and let memory fill in the rest as you go.
Where do I find the instructions box in Claude?
Click your initials in the bottom-left corner, open Settings, and look for the section called Instructions for Claude. The label has been renamed before, so if you do not see those exact words, look for the personalisation or instructions option under Settings.
Should I write a long, detailed set of instructions?
No. A short, clear note works better than a long one. A wall of rules pulls Claude in too many directions and can make answers worse, so keep it to the few things that actually change how it replies to you.
Set yours now
Open Settings, paste the template, and put one real line about yourself in the first field. The next chat you start will already sound more like you, and you never have to type any of it again.