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← All writingPublished October 20, 2026

How to train AI on your writing style

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To train AI on your writing style, pick a handful of pieces that sound most like you, turn them into a short voice guide that says what makes them yours, and give the guide and the pieces to Claude or ChatGPT as standing instructions. Then test its drafts against your own writing and fix the guide wherever a draft slips.

None of this changes the model itself, which reads your guide every time it writes, so the guide matters more than the tool you pick.

Choose the samples that are really yours#

Start with five to ten pieces you wrote yourself and would happily put your name to today. Recent work beats old work, because your style moves over the years, and the AI should copy where you are now.

Leave out anything an editor rewrote, anything someone else drafted for you, and anything you wrote to fill in a template, since those carry other people's habits. Mix the formats you publish, such as a post, a newsletter and an email, so the guide learns what stays the same across all of them.

Pick one or two you're proudest of and note why. That note often turns into the most useful line in the guide.

Turn them into a voice guide#

A voice guide is a short document that describes how you write, clearly enough that someone who has never met you could follow it. It says who you write for, how you sound, the words you use and the ones you never use, how your sentences run, how you open and close, and what you'd never do.

The best guides show rather than describe. Friendly and professional tells a model almost nothing, and one sentence of yours tells it a lot. So under each point, quote a line from your samples, and where it helps, a line that sounds wrong next to it.

Here's a short one for a made-up newsletter writer called Jane.

  • Who I write for. Owners of small service businesses, busy and wary of hype.
  • How I sound. Plain, warm and a little dry, and I say what I think in the first line, like Most proposals lose the deal on page one, never like In today's fast-paced business landscape.
  • Words I use. Client, the work, the price, the call.
  • Words I never use. Leverage, unlock, game-changer, delve, synergy.
  • Sentences. Mostly short, one idea each, with one question to the reader per piece at most.
  • Openings and endings. A claim or a small story to open, never a definition, and one thing the reader can do today to close.
  • Never. Exclamation marks, emojis, or In conclusion.

You can ask Claude or ChatGPT to draft a first version from your samples, then correct it by hand. It notices patterns you can't see in your own writing, and misses the reasons behind them, which only you know.

Where the guide lives in Claude#

The simplest home is a project. Create one from Projects in the sidebar, click Set project instructions and paste your guide, then add your sample pieces to the project's knowledge with the + button. Every chat in that project follows the instructions and can read the samples.

If you want the guide wherever you write in Claude, without opening a project first, make it a skill. A skill is a folder with a file called SKILL.md, which Claude loads only when a task matches its description. The file opens with a name in lowercase with hyphens, such as janes-writing-voice, and a description of when to use it, such as Write in Jane's voice for any newsletter, post, email or article she asks for. Your guide goes under them, and you upload the folder as a ZIP under Customize, then Skills. How to write good Claude skills goes further.

Older guides send you to Claude's Styles menu for this. Anthropic has since turned styles into skills, so a custom style made from your samples now waits under Customize, then Skills, switched off until you turn it on, and you call it with its name and -style, such as /janes-voice-style.

A short version of the guide, a few lines on how you sound and what you never do, can also go in Instructions for Claude in your Settings, which applies to every conversation.

Where the guide lives in ChatGPT#

The same idea works in a ChatGPT project. Select New project in the sidebar, upload your samples as files, then open the project's ••• menu, select Project settings and paste the guide as its instructions. Project instructions apply only inside that project, and they override your general custom instructions.

For a short version that applies to every chat, go to Settings, then Personalization, and paste it into Custom Instructions. Free and Go accounts can save 1,500 characters there, and Plus, Pro, Business, Enterprise and Education accounts 5,000, so it fits the summary of the guide and seldom the whole thing.

Older guides tell you to build a custom GPT for this. OpenAI is retiring custom GPTs, and personal accounts can no longer create new ones, so a project is the place for it now.

Test the drafts against your own writing#

Ask for a piece on a topic you've already written about, then put the draft beside your own version and read both out loud. Mark every line you'd never say.

For each mark, change the guide and leave the draft. Add the rule that was missing, or a line of yours that shows the right way. A correction made in one chat helps that chat, and a correction made in the guide helps every draft after it.

Run it again with a new topic, and keep going until three drafts in a row need only the edits you'd make to a first draft of your own. Then check in every month or so, because old habits creep back in.

Keep a person on the last read#

Even when the drafts are good, a person who knows your voice reads everything before it goes out. A model writes with confidence about facts it got wrong, and it drifts back toward its own habits a little at a time, so the person reading is what keeps both from reaching your readers.

A voice guide in practice#

Pathless Presence is a community for mindful people, and its copy had to stay gentle, never preachy and never sounding like a guru handing down enlightenment. It was written with a poet, and the poet's dos and don'ts became the instructions behind the content agent I built into its admin panel. The agent writes posts for every channel in the brand's voice, and the team can change what it knows and how it speaks without a developer.

A poet's dos and don'ts, written down as instructions the team can keep changing, are a voice guide at work. If you'd rather have yours built and set up for every channel, send me your best posts.

Sources#