Set Up ChatGPT Custom Instructions for Client Brand Voices

Before opening ChatGPT, collect these from your brief or brand guide:

• Tone adjectives (3–5): e.g., "confident, direct, conversational, no-nonsense"
• Vocabulary rules: Words they use / words they avoid. e.g., "Say 'people' not 'users,' say 'easy' not 'seamless'"
• Sentence structure preference: Short punchy sentences? Long complex ones? Mix?
• Things to never do: "Never use exclamation points," "never say synergy or leverage," "avoid bullet lists — use paragraphs"
• Audience description: Who the content is for, in one sentence

What you should see: A short notes document with these 5 elements captured.

1. Log into chat.openai.com
2. Click your profile picture (bottom left) → "Customize ChatGPT"
3. Two text fields appear: "What would you like ChatGPT to know about you?" and "How would you like ChatGPT to respond?"

What you should see: Two large text input boxes.

In the second box ("How would you like ChatGPT to respond?"), write your client-specific brand voice instructions. Use this template:

I'm a copywriter working on content for [Client Name]. Apply these brand voice rules to every response:

TONE: [adjective 1], [adjective 2], [adjective 3]. Never [tone to avoid].
VOCABULARY: Always use "[word A]" instead of "[word B]." Never use: [list jargon words].
SENTENCES: [Short and punchy / Long and detailed / Mix short and medium]. Max [X] words per sentence.
AUDIENCE: [One sentence describing the target reader].
CONTENT RULES: [Any specific do's and don'ts].
EXAMPLE: Here's a paragraph in our brand voice: "[paste a real approved example]"

What you should see: A filled-in brand voice template in the second text box.

Troubleshooting: If ChatGPT still sounds generic after setting instructions, add a real example paragraph at the end ("Here's how we actually sound:"). Showing is more effective than describing.

Click "Save" → start a new conversation → give ChatGPT a simple task: "Write a 2-sentence product description for [product]."

Read the output and check: Does it sound like the client? Does it use the right vocabulary? Does it avoid the banned words?

What you should see: A response that feels noticeably different from ChatGPT's default voice — shorter if you specified short, more casual if you specified conversational.

If the output doesn't sound right, go back to Custom Instructions and adjust. The most common fixes:

• Add more "never say" vocabulary examples
• Add a second real example paragraph
• Make the audience description more specific: "They're overwhelmed marketing managers who don't have time for theory — they want practical, fast advice"

Troubleshooting: Custom Instructions apply to ALL your ChatGPT conversations while they're active. To switch clients, you need to update the instructions. See the tip below about browser profiles.