Short answerA Custom GPT is one configured assistant. An OpenAI plugin is an installable package that can contain skills (written workflows), an MCP server (connections to outside systems), or both. Recipients install plugins, and you need a permission to share them.
Side by side
| Custom GPT | Plugin | |
|---|---|---|
| What it is | One configured assistant with instructions and files | A package of skills, an MCP server, or both |
| Instructions | The GPT's instruction field | A skill: a folder with a SKILL.md file describing a repeatable workflow |
| Outside connections | Actions | An MCP server exposing tools with schemas and authentication |
| Sharing | Share the GPT | Share a plugin with people or groups; recipients install it (admins can install for them). Needs the Share plugins permission |
| Using it | Open the GPT | Select via @ mention or the + menu; it does not necessarily run on every request |
Sources: OpenAI's plugin documentation and migration guide, checked October 18, 2026.
Why it matters for migration
Because a plugin is a package, your GPT's pieces map to different parts: instructions become a skill, files become reference files, and Actions must be rebuilt as an app or MCP server. Walkthrough: migrating to a plugin. If you would rather leave ChatGPT, see alternatives.
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Sources
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