Custom GPT vs Claude skills: what's different, and how to move

Side by side

From OpenAI's retirement FAQ (read through search-result text) and the Claude Help Center, 5 November 2026.

A worked example: moving a GPT

Illustration: a made-up business. An HR consultant has a "Job ad writer" GPT: 400 words of instructions, a style guide PDF, and an action that posted drafts to her applicant tracking system.

• Instructions: she adds a name (job-ad-writer), a description ("Use when writing or rewriting a job ad from a role brief"), and turns her paragraphs into seven numbered steps.
• Style guide: goes into the skill's folder as a reference file.
• The action: doesn't move. She now copies the finished ad into the tracker by hand; posting through a connector is a later project.

The difference shows on day one: she no longer opens the GPT. She types "job ad for a part-time bookkeeper" in any Claude chat, and the skill loads. The same file also works in ChatGPT.

Move a GPT into a skill

1. Copy the GPT's instructions and download its knowledge files.
2. Write a name and a "use when" description; this is what makes the skill load by itself.
3. Turn the instructions into numbered steps with one example.
4. Put knowledge files in the folder, and list any actions to rebuild as connectors.
5. Test in Claude and ChatGPT, then share it before 11 December.

The free GPT to skill converter does steps 2 and 3 in your browser. For the sharing side of the retirement, see keeping your custom GPT shared after it retires.

Next step: one skill for every AI

Once your GPTs are skills, your team can use them from Claude and ChatGPT alike, but only if everyone reads the same copy. The cheapest way to share AI prompts and skills compares the options, and ChatGPT skills vs Claude skills covers how each product handles them.

Questions

What's the difference between a custom GPT and a Claude skill?

A custom GPT is a separate chatbot with its own instructions and files that you open and talk to. A Claude skill is a set of instructions Claude loads by itself, in any chat, when your request matches its description. You don't switch to it; you just ask.

Can I convert a custom GPT into a Claude skill?

Yes, the instructions move over almost as they are: add a name and a 'use when' description, and turn the instructions into steps. Knowledge files can go in the skill's folder. Actions don't move; they need a connector.

What happens to custom GPTs on 11 December 2026?

OpenAI says custom GPTs stop running then. Their instructions become a skill inside a ChatGPT plugin, which starts private, and custom actions have to be rebuilt.