How to Make AI Write Like You (November 2026)

You can spot AI writing a mile off. An em dash in every sentence, "it's not just a tool, it's a game-changer", or a post about "the ever-evolving landscape" of something. The second I see it, I switch off.

This guide shows you how to make AI write like you in ChatGPT, Claude and Codex. There are seven levels. Level 1 takes two minutes on a free plan. Level 7 is what I use every day, where every AI tool I touch already knows how I write. Pick the level that suits you and stop there if you like.

Why AI writing is so easy to spot

AI writes whatever is most likely to come next, so it reaches for the same moves every time. The em dash (that long hyphen there isn't even a key for). The "it's not X, it's Y" sentence. Words like delve, elevate and seamless. Once you know them, you see them everywhere.

And people are sick of it. On 30 July 2026 LinkedIn added a "Seems like AI slop" button to posts (TechCrunch covered the launch). LinkedIn's own figures say over a million people clicked it in the first few weeks, and content it classed as slop got 40% fewer views. In a Harris Poll shared at Cannes Lions in June, 73% of people said they trust an advert less if they suspect AI made it.

My view is simple. If your email or post doesn't sound like you, the reader might as well have asked AI themselves.

One thing before we start. None of this means you stop editing. AI is brilliant at a first draft, and the draft is still yours to fix before anyone else reads it.

I made a full video of this, with every step on screen:

Level 1: feed it your writing

This works in any AI, free plans included.

Open a notes app and collect 5 to 10 pieces of writing that are 100% you. Your LinkedIn posts are a good source: open your profile, click show all posts and scroll back to before the end of 2022, when ChatGPT came out. Anything from then has no AI in it. Old emails, Slack messages and X posts work too.

Then open a new chat and paste this prompt, with your writing underneath:

Below are some pieces of writing I wrote myself. Don't write anything new yet.

Study them and list the patterns in how I write: how I open, how long my sentences are, words and phrases I use a lot, my punctuation habits, how I end, my tone, and anything I never do.

Then write it all up as a "Voice profile" I can copy and reuse: one short paragraph describing my voice, a bullet list of rules, and 3 example sentences in my style. Use UK English.

[PASTE YOUR WRITING HERE]

The first line matters. You're asking it to study you, not write anything yet.

Mine surprised me. I use two dots for a pause.. rather than three, and I end a lot of posts on a question. Copy the voice profile it gives you into your note and call it something like "My voice profile". That's your voice in a box.

Level 2: the don'ts list

Telling AI what not to do matters as much as telling it what to do, because the tells are the bits people notice. Under your voice profile, type "Don'ts" and list what you never want to see. Here's a starter list you can copy:

• No em dashes or en dashes
• No "it's not X, it's Y"
• No "delve", "landscape", "elevate", "seamless", "game-changer", "unlock"
• No "Here's the thing" or "Let that sink in"
• No dramatic one-line endings

Now put it to work. Next time AI writes something for you, open a new chat and paste this:

Here's my voice profile and my don'ts list. Rewrite the text below so it sounds like me.

Follow my patterns, break none of the don'ts, keep every fact, and don't add anything I didn't say.

VOICE PROFILE:
[PASTE]

DON'TS:
[PASTE]

TEXT:
[PASTE]

A real one from me. An AI draft of one of my LinkedIn posts opened with "3 years ago I made a small decision that's quietly saved me a few hundred quid since." What I posted was "3 years ago I made a decision that's saved me quid since." Small, quietly, a few hundred: all filler, so out they went.

The problem with levels 1 and 2 is that you're pasting your profile in every time. Level 3 fixes that.

Level 3: ChatGPT custom instructions

In ChatGPT, click your name bottom left, then Settings, then Personalization. Make sure Enable customization is switched on. Paste your voice profile and your don'ts into the Custom instructions box and save.

Every chat now uses it, old ones included, on the web, the desktop app and your phone. No more pasting.

How much fits depends on your plan. Free and Go hold 1,500 characters. Plus (about £20 a month) and the higher plans hold 5,000, which OpenAI raised from 1,500 in July 2026 (OpenAI's help page has the current limits). If you're on free, cut your profile down to the rules that matter most.

Two more things on the same page. There's a separate box for Codex, so ChatGPT's coding agent gets the same rules. And under Writing there's a "Reference my writing style" switch, which lets ChatGPT learn from your chats, files and any apps you connect, like Gmail and Slack. I've only just turned it on, so I can't tell you how good it is yet. If you'd rather not give AI your inbox, leave it off. The custom instructions do most of the work anyway.

Level 4: a writing-voice skill

Custom instructions only live in ChatGPT, and I don't only use ChatGPT. A skill does.

A skill is a folder with a text file inside called SKILL.md: a short instruction manual the AI loads when you ask for it, or when it can tell the job needs it. It's markdown, which is plain text with a few symbols for headings. Nothing scary, and you don't have to write it yourself. Your AI can build it for you.

In Claude: open a new chat and type "Make me a skill called my writing voice from this voice profile", then paste your profile and don'ts. Claude builds it, you click save, and it sits in your settings ready for any chat. Skills work on every Claude plan, free included, as long as code execution is switched on (Anthropic's guide to skills).

In Codex: open the hidden .codex folder in your home folder, then skills, and make a folder called my-writing-voice. Inside it, make a file called SKILL.md and paste your profile and don'ts in. In Codex, type $ and start typing the name to pick it.

In ChatGPT: skills are there now too, under Plugins in the sidebar. This matters because OpenAI is retiring custom GPTs and pointing people to plugins and skills instead, so a voice GPT isn't the way to go anymore.

You can call a skill by name, or just ask the AI to use it. One habit of mine: if it's not obvious the skill was used, I ask "Did you use my writing voice skill for that?" It has said yes every time so far.

I use two skills for nearly everything I write. One is my voice, built from over 100 of my own LinkedIn posts. The other is humanizer, a free skill built from Wikipedia's list of signs of AI writing. It hunts down 25 patterns and takes them out. My voice skill makes it sound like me, and humanizer strips out whatever AI tells are left.

Level 5: AGENTS.md, one file every AI reads

This is the big one, and it's for anyone using coding agents like Claude Code or Codex. It's more technical, so skip it if you're not there yet. If you want to get there, my guide to setting up AI on your computer takes about 15 minutes.

AGENTS.md is a plain text file of instructions that coding agents read at the start of every session. It's become the standard most of them share (agents.md lists the tools that support it): Codex reads it, Cursor reads it, and Gemini CLI can with one setting.

For Codex: open the hidden .codex folder in your home folder and make a file called AGENTS.md. Add a heading, "Writing rules", and paste your voice profile and don'ts under it. Add one more line saying every draft gets a human edit before it goes out. Save it, and every Codex session starts with it.

For Claude Code: Claude Code reads its own CLAUDE.md files. Open your global one (~/.claude/CLAUDE.md, which is hidden by default on a Mac) and add one line at the top: an @ sign followed by the path to your AGENTS.md file. That tells Claude Code to read the same file. Newer versions of Claude Code will also read an AGENTS.md sitting in a project folder.

Now you edit your rules in one place and every tool writes the same way. That's what people mean by model agnostic, and I'm a big believer in it. If a better model comes out from another company next month, I switch, and it writes like me from day one.

Level 6: a voice per folder

You can give one folder its own voice too. Make an AGENTS.md (or a CLAUDE.md if it's only for Claude) inside the project folder and write in it how that project should sound. The tools read your global file first, then the one in the folder you're working in.

At my agency we have a blog writing folder where every client has their own voice profile. One client sells furniture, so theirs is practical and written for someone choosing what to buy. Same AI, but it writes in their voice in their folder and in mine everywhere else.

Level 7: teach it from your edits

This is the level that makes the rest better over time. Every time you rewrite an AI draft, you've shown it exactly what it got wrong. Next time you edit something, paste this into a new chat:

Here's what you wrote and here's what I sent after editing it. List what I changed and why, then update my voice profile with any new rules.

YOUR DRAFT:
[PASTE]

WHAT I SENT:
[PASTE]

Copy the new rules into your voice profile, or your AGENTS.md if you have one.

What I do is simpler again. When I've rewritten something, I paste what I wrote into my AI and say something like "Update the relevant skills and my global and local MD files with this, to help with my writing style now and in future." It works out where each rule goes and updates them for me. That "small decision that's quietly saved me a few hundred quid" line ended up as a rule in my AGENTS.md exactly this way.

Since I set this up I edit less, my emails go out faster and the website copy drafts for the sites we build are miles better than they were.

Which level should you start at?

You still edit it

This gets you a better first draft. It doesn't replace you. Read it, change it and put your own thinking in, because that's what people come to you for. If you want a second job for AI after this one, talking instead of typing is the next thing I'd set up, and keeping one AI project per part of your life stops you repeating yourself in every chat.

Questions people ask

Can ChatGPT learn my writing style?

Yes. Paste 5 to 10 pieces of your own writing into a chat and ask it to list your patterns as a voice profile (the level 1 prompt above), then save that profile in Settings, Personalization, Custom instructions. Every chat uses it from then on.

How do I stop ChatGPT using em dashes?

Put it in your don'ts list and save the list in custom instructions: "No em dashes or en dashes. Use commas, full stops or colons instead." It will still slip one in now and then, so read the draft before you send it.

How many writing samples does AI need?

5 to 10 pieces is enough to start, as long as they're 100% you. My voice skill is built from over 100 LinkedIn posts, but it started with far fewer.

What's the difference between custom instructions and a skill?

Custom instructions apply to every ChatGPT chat automatically and stay in ChatGPT. A skill is a folder with a SKILL.md file that loads when it's needed, and it works in Claude, Codex and ChatGPT, so one voice skill follows you between tools.

Do I need a paid plan?

No. Levels 1 and 2 work on any free plan, and ChatGPT's free plan has custom instructions too, with a 1,500 character limit. Plus and above get 5,000.

Will people still be able to tell I used AI?

Less often, but it isn't a disguise. Read it, change it and add what only you know.

What is AGENTS.md?

A plain text file of instructions that coding agents read at the start of every session. Codex reads a global one from the .codex folder in your home folder, Cursor reads one in a project folder, and Claude Code can be pointed at it with one line in your CLAUDE.md.

What's next

I share one AI setup like this every Sunday in The Growth Toolkit, the ones I use in my own business, with the prompts and the steps to copy. There are more ready-to-paste prompts in my prompt library, and the AI tools I rate for running a business if you're still picking your stack.

Mike McDonnell. I write The Growth Toolkit, a free Sunday email on making more profit with AI, with the setups I use in my own business explained in plain English.