Custom Instructions on Grok, Claude, and ChatGPT — Setup Guide With Templates

📖 AI Instructions Complete Guide — View all▶ Part 1: Stop Repeating Yourself to AI (this post) Part 2: Manage AI Instructions Like Files Part 3: 7 Common Mistakes That Ruin Your AI Instructions Part 4: When AI Ignores Your Instructions Part 5: Where Does AI Store Your Conversations Part 6: Send AI Tasks From Your Phone

“I already told you this in our last chat.” If you’ve ever said that to an AI, you need custom instructions.

Once you start using AI chatbots for real work, you hit the same wall. “I’m a project manager,” “Use formal tone,” “Format as a table” — you type these every single time. Every new conversation starts from zero.

The fix already exists on every major platform. Developers call it CLAUDE.md — a file that tells the AI your project’s rules once. But you don’t need to code. The same concept works in your browser, right now.

What Are AI Custom Instructions

Custom instructions let you write down everything the AI should always know about you and your preferences — once. Every new conversation starts with that context already loaded.

In the developer world, a file called CLAUDE.md serves this purpose. It stores project rules, coding style, and constraints so the AI references them automatically. But for anyone using AI through a web browser, each platform offers its own version of the same idea.

The core principle is identical: write your context once, and the AI remembers it in every conversation.

Claude — Project Instructions

Claude (claude.ai) manages instructions through its “Projects” feature.

How to set it up:

1. Go to claude.ai and find “Projects” in the left sidebar 2. Click “New Project” and give it a name (e.g., “Work Reports,” “Blog Writing”) 3. Open the project settings and enter your instructions 4. Optionally upload reference files — style guides, templates, sample documents

Key features:

• Each project gets its own separate instructions
• Profile preferences (global) and project instructions (per-project) are layered — global settings apply first, then project instructions add context on top
• You don’t need to repeat general preferences like “be concise” in every project
• Free plan users get up to 5 projects

Writing tips:

Aim for 200 to 500 words. Too short and the AI has nothing to work with. Too long and parts get ignored in extended conversations. Structure your instructions around four areas: Profile (who you are), Voice (how to write), Rules (what not to do), and Format (output structure).

ChatGPT — Custom Instructions + GPTs

ChatGPT offers two paths to set instructions.

Custom Instructions

How to set it up:

1. Go to chatgpt.com and click your profile in the bottom left 2. Select “Customize ChatGPT” 3. Fill in two fields:

• “What would you like ChatGPT to know about you?” — your role, background, goals
• “How would you like ChatGPT to respond?” — tone, format, length preferences

Key features:

• Once set, they apply to every new conversation automatically
• You can toggle them on or off per conversation
• They work alongside ChatGPT’s memory feature — memory learns from conversations, custom instructions are rules you set explicitly

GPTs (Custom GPTs)

GPTs let you build a purpose-specific AI assistant.

How to set it up:

1. Go to chatgpt.com, click “Explore GPTs,” then “Create” 2. Enter a name, description, and detailed instructions 3. Upload reference files 4. Toggle capabilities like web search and image generation

Custom Instructions vs GPTs:

Feature	Custom Instructions	GPTs
Scope	All conversations	Only within that GPT
Memory	Uses saved memory	No memory (fresh each time)
File uploads	No	Yes
Sharing	No	Shareable via link
Best for	General preferences	Task-specific workflows

If you have a repeating workflow — writing reports, translating documents, reviewing code — build a GPT for it. Use Custom Instructions for your overall conversation style.

Grok — Custom Instructions + Workspaces

Grok (grok.com or the X app) also supports custom instructions.

How to set it up:

1. Go to grok.com and click the settings gear icon 2. Find “Custom Instructions” and enter your preferences

Key features:

• Character limit is 4,000 characters (reduced from 12,000 in early 2026)
• You can set different instructions per Workspace
• Custom Agents let you configure up to 4 role-specific AI agents

Important note:

The character limit is the tightest of the three platforms. Keep instructions brief and direct. Short rules like “never use bullet points” or “always include sources” work better than long paragraphs.

Platform Comparison at a Glance

Feature	Claude	ChatGPT	Grok
Where to set	Project instructions + Profile	Custom Instructions + GPTs	Custom instructions + Workspaces
Per-project separation	Projects	GPTs	Workspaces
File uploads	Yes (project knowledge)	Yes (GPTs)	Yes (Workspaces)
Character limit	Generous	Generous	4,000 characters
Free tier	5 projects	Custom Instructions available	Supported
Memory integration	Profile preferences	Memory feature	Limited

Copy-Paste Templates

Adapt these templates to your situation and paste them into your platform’s instruction field.

For Work Reports

I am a project manager at a tech company.

Tone: Professional and concise. No filler words or unnecessary qualifiers.

Format: Lead with the key takeaway, then supporting details. Use tables and bullet points whenever possible.

Rules: – Minimize speculative language (“might,” “could potentially”) – Always include units and sources for numbers – End with a “Next Steps” section

For Translation (Korean to English)

Translate Korean blog posts to English.

Style: Read like it was written in English originally. American English.

Rules: – Romanize Korean proper nouns, add Korean in parentheses on first mention – Break long sentences into natural English rhythm – Add brief context for Korea-specific concepts – Convert formal Korean speech levels to second-person “you”

Three Principles for Writing Good Instructions

1. Start with your role

“I am a 3-year PM” and “I am a student learning to code” produce completely different responses from the same AI. One line of context changes everything.

2. Say what NOT to do

“Don’t write introductions longer than two sentences” is more effective than “be concise.” Constraints give the AI clear boundaries.

3. Include one example

Instead of “format as a table,” show the exact table structure: “| Item | Description | Notes |”. One concrete example beats a paragraph of abstract instructions.

Wrapping Up

If you’re repeating the same context to AI every conversation, that’s your signal to set up custom instructions.

Developers write CLAUDE.md files to give AI project context. The same principle works in your browser — Claude calls it Project Instructions, ChatGPT calls it Custom Instructions and GPTs, Grok calls it Custom Instructions and Workspaces. Different names, same idea.

Set it up once, and every conversation starts with your AI already knowing who you are and how you work. Grab a template from above and try it right now.

Once you’re comfortable with web-based instructions, there’s a next level. With VS Code, you can split instructions into separate files, organize them by project, and manage them like a pro — no coding experience required. We’ll cover that in the next post.