Day 18 of 28 · ChatGPT Course

Custom GPTs

⏱ 7 min 📊 Medium

ChatGPT is powerful out of the box, but what if you could create a version of it that is purpose-built for a specific job? One that already knows your industry terminology, follows your exact guidelines, and has access to your reference documents every single time?

That is what Custom GPTs are. They are your own tailored AI assistants, built on top of ChatGPT, with custom instructions, uploaded knowledge files, and optional tool integrations. No coding required.

Today you will learn how to create a Custom GPT from scratch, configure it for real use cases, and even share or publish it for others to use.

Anatomy of a Custom GPT — instructions, knowledge files, tools, and publishing

A Custom GPT combines instructions, knowledge, and tools into a specialized assistant.

What is a Custom GPT?

A Custom GPT is a specialized version of ChatGPT that you configure for a specific purpose. It has three layers of customization:

Instructions -- persistent rules that define how the GPT behaves. These are like system-level prompts that apply to every conversation. You might instruct it to always respond in a certain tone, follow a specific framework, or ask clarifying questions before answering.

Knowledge files -- documents you upload that the GPT can reference. These could be style guides, product documentation, FAQs, research papers, or any other reference material. The GPT searches these files when answering questions.

Tools -- built-in capabilities you can enable or disable, such as web browsing, image generation (DALL-E), and code execution (Code Interpreter). You choose which tools your GPT can use.

The result is an AI assistant that feels like it was custom-built for your exact needs.

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ChatGPT

online

I want to build a Custom GPT that helps my customer support team answer product questions. How do I do that?

Here's how to build a Customer Support GPT step by step: **1. Go to "Create a GPT"** Click your profile picture > "My GPTs" > "Create a GPT" **2. Configure the instructions:** "You are a customer support assistant for [Your Company]. Always be friendly and professional. Answer questions using only the uploaded knowledge base. If you don't know the answer, say 'I'll need to escalate this to our team' and provide the support email. Never make up product features or pricing." **3. Upload knowledge files:** - Product documentation (PDF or text) - FAQ document - Pricing page content - Return/refund policy - Troubleshooting guides **4. Set capabilities:** - Enable web browsing (for checking order status pages) - Disable DALL-E (not needed) - Enable Code Interpreter (for analyzing support data) **5. Test it** with real customer questions before sharing with your team.

↻ Replay conversation

Knowledge Check

What are the three layers of customization in a Custom GPT?

A

Speed, accuracy, and personality

B

Input, processing, and output

C

Name, icon, and description

D

Instructions, knowledge files, and tools

Custom GPTs are built on three pillars -- instructions (how it behaves), knowledge files (what it knows), and tools (what it can do). Together, these allow you to create a specialized assistant tailored to any use case without writing code.

Building a Custom GPT step by step

Let's walk through the actual creation process:

Step 1: Open the GPT Builder. Navigate to "My GPTs" and click "Create a GPT." You will see two options: a conversational builder (where you describe what you want and ChatGPT helps you configure it) and a manual configuration panel.

Step 2: Write your instructions. This is the most important step. Your instructions define the personality, rules, and behavior of your GPT. Be specific and thorough:

- Define the role: "You are a technical writing assistant for a software company."

- Set the tone: "Write in a clear, concise style. Avoid jargon unless the user uses it first."

- Add constraints: "Never reveal internal pricing. Always suggest the user contact sales for custom quotes."

- Include workflows: "When asked to review a document, first identify the audience, then check for clarity, then suggest improvements."

Step 3: Upload knowledge files. Drag and drop your documents. The GPT will automatically index and search them when answering questions. Supported formats include PDF, Word documents, text files, spreadsheets, and more.

Step 4: Configure tools. Toggle on the capabilities your GPT needs. Web browsing for up-to-date information. DALL-E for image generation. Code Interpreter for data analysis and calculations.

Step 5: Test and iterate. Before sharing, test your GPT with the kinds of questions it will actually receive. Refine instructions based on where it falls short.

Knowledge Check

Which step is the most important when building a Custom GPT?

A

Uploading as many files as possible

B

Enabling all available tools

C

Choosing an icon and name

D

Writing specific, thorough instructions that define behavior, tone, and constraints

Instructions are the foundation of a Custom GPT. They determine how it behaves, what tone it uses, what rules it follows, and how it handles edge cases. Vague instructions produce vague results. Specific, well-written instructions produce consistently excellent outputs.

Use cases that work well

Custom GPTs are ideal for any task that you do repeatedly with specific requirements:

Customer support bot. Upload your product docs, FAQs, and policies. Instruct it to answer only from the knowledge base and escalate when unsure. Share with your support team.

Writing assistant. Upload your style guide and past writing samples. Instruct it to match your voice, suggest edits, and flag inconsistencies. Perfect for maintaining brand voice across a team.

Data analyzer. Upload data templates and reporting guidelines. Enable Code Interpreter so it can process spreadsheets, run calculations, and generate charts.

Onboarding guide. Upload your company handbook, org chart, and process documents. New employees can ask it anything about how the company works.

Sales assistant. Upload product specs, competitive comparisons, and pricing frameworks. It helps sales reps quickly find answers during prospect calls.

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ChatGPT

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I built a Custom GPT for my content team. Can I share it with people outside my organization?

Yes! You have three sharing options: **1. Private (Only Me)** Only you can access it. Good for personal productivity tools. **2. Anyone with the Link** Share a unique URL with specific people -- your team, clients, or collaborators. They need a ChatGPT account to use it. **3. Public (GPT Store)** Publish it to the GPT Store where anyone can discover and use it. You'll need to: - Verify your builder profile - Add a clear description - Ensure it follows OpenAI's usage policies For your content team, "Anyone with the Link" is probably best. They get access without it being public.

↻ Replay conversation

Publishing to the GPT Store

If you build a Custom GPT that could help others beyond your organization, you can publish it to the GPT Store -- a marketplace where anyone can discover and use Custom GPTs.

To publish:

1. Verify your builder profile -- confirm your name or brand

2. Write a compelling description -- explain what your GPT does, who it is for, and what makes it useful

3. Set the visibility to Public

4. Submit for review -- OpenAI checks that it follows usage policies

The GPT Store has categories like Writing, Productivity, Research, Programming, Education, and more. Popular GPTs appear in featured sections, driving organic discovery.

For teams and organizations, ChatGPT Enterprise and Team plans allow you to share Custom GPTs within your workspace. Team members can use them without them being publicly listed.

Knowledge Check

How can you share a Custom GPT with your team without making it public?

A

Email the instructions and files to each team member

B

You cannot -- all Custom GPTs are public

C

Share a unique link that gives access to anyone who has it

D

Publish it to the GPT Store with a password

The "Anyone with the Link" sharing option lets you give access to specific people without publishing to the GPT Store. Recipients need a ChatGPT account to use it. This is ideal for internal team tools, client-facing assistants, or private communities.

Final Check

What happens when a Custom GPT receives a question that is not covered by its uploaded knowledge files?

A

It crashes and shows an error

B

It automatically searches the web for an answer

C

It always makes up a plausible-sounding answer

D

Its behavior depends on your instructions -- you can tell it to say "I don't know" or escalate, rather than making up answers

This is exactly why instructions matter. Without explicit guidance, the GPT might hallucinate an answer. But if your instructions say "only answer from the uploaded knowledge base" and "say 'I need to escalate this' when unsure," it will follow those rules. You control the fallback behavior.

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Day 18 Complete

"Custom GPTs let you build a specialist AI assistant for any job. Write clear instructions, upload your knowledge, and share it with the people who need it."

Tomorrow — Day 19

ChatGPT Agent

Discover ChatGPT's agent mode -- an AI that can browse the web, fill forms, and complete real-world tasks for you.

Continue to Day 19 →