A skill is a reusable, shareable workflow that tells ChatGPT how to do a specific task. Rather than starting from scratch each time, you define the process once so it can be applied reliably whenever the task comes up.

Skills are most useful when getting a good output from ChatGPT depends on following a repeatable approach—especially when tasks involve multiple steps, structured formats, or specific requirements.

A SKILL.md file is the skill’s playbook: a plain-text set of instructions that tells ChatGPT how to run a workflow consistently. It’s written in Markdown (the “.md” part), a lightweight formatting style that uses simple symbols—like "#" for headings and "-" for lists—so the file is easy to read and edit in most tool.

Because it’s plain text and Markdown-based, SKILL.md is portable. It can be shared, versioned, and reused across tools. It’s also designed as an open standard⁠(opens in a new window), so similar patterns may appear in other AI apps and platforms.