Custom GPT: Definition and How to Create Your Own
A Custom GPT is a ChatGPT assistant pre-configured by a user with a specific system prompt, knowledge files, and optionally Actions (API calls), distributed via the OpenAI ecosystem.
Full definition
Custom GPTs (or customized GPTs) were launched by OpenAI at the end of 2023 and are one of the pillars of ChatGPT's ecosystem strategy. A Custom GPT is essentially a pre-parametrized instance of the ChatGPT model, on which its creator has defined:
- A precise behavior via system instructions (role, tone, constraints) - A knowledge base (uploaded PDF, .docx, .csv files) - Extended capabilities: web browsing, image generation, Python code execution - Custom Actions (calls to external APIs via OpenAPI)
Custom GPTs are accessible through the GPT Store (OpenAI's public marketplace), shareable via a private link, or available only to their creator. They allow packaging a recurring use case into a clickable assistant, without having to rewrite the prompt each time. It is OpenAI's equivalent of Claude Skills and Google's Gemini Gems.
Etymology
The name Custom GPT (or customized GPT) borrows the acronym from the GPT model (Generative Pre-trained Transformer), with the addition of the qualifier Custom to emphasize customization by the end user, not by OpenAI.
Concrete examples
Custom GPT for business personal use
Create a Custom GPT "B2B Sales Coach" trained on 10 reference books (SPIN Selling, Challenger Sale, etc.) that helps me prepare my discovery interviews with prospects.
Custom GPT with Actions and grounding
Configure a "Legal Assistant" GPT that queries a database of French legal articles via an Actions API, and only responds by citing its sources.
Custom GPT to automate content production
Build a "Brand voice writer" GPT with my editorial charter as knowledge file, to generate LinkedIn posts in my exact tone.
Practical usage
To create a Custom GPT, go to chat.openai.com and open the GPT Builder. The conversational interface guides creation: name, description, behavior instructions, adding knowledge files, tool activation. The GPT can then be tested directly, shared privately, or published on the GPT Store. Public distribution requires a verified OpenAI account.
Related concepts
FAQ
What is the difference between a Custom GPT and a Claude Skill?
Can you monetize a Custom GPT?
Do you need to be a developer to create a Custom GPT?
See also
How to use this prompt
- Copy the prompt with the button above.
- Paste it into ChatGPT, Claude or your favorite AI assistant.
- Replace the bracketed variables with your details, then refine the result.
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