The short answer
An AI skill is a saved, reusable package of instructions, with a name and a short description of when to use it, that an AI assistant loads when your request matches. Anthropic's Claude offers skills on every plan from Free to Enterprise. In OpenAI's ChatGPT, skills live inside plugins, which replace custom GPTs on 11 December 2026. Google's Gemini skills replace Gems, which become read-only on 17 November 2026.
| What it is | Saved instructions (and optional files) an assistant loads when relevant |
|---|---|
| Claude | Customize, then Skills; Free, Pro, Max, Ultra, Team and Enterprise; needs code execution |
| ChatGPT | Skills live inside plugins; Plugins in the sidebar; creation via Plugin Creator |
| Gemini | Customize, then Skills; no subscription needed; 18 or over |
| Replaces | Custom GPTs (retire 11 December 2026) and Gems (read-only 17 November 2026) |
| Core file | SKILL.md with a name and a description |
| Not the same as | Fine-tuning; the model does not change |
What an AI skill is, in plain English
An AI skill is a saved, reusable set of instructions that teaches an AI assistant how to do one specific job your way. At its simplest it is a short text file with three parts: a name, a one-line description of when to use it, and the instructions themselves, such as the steps to follow, the format to produce and the mistakes to avoid. A skill can also carry reference files (a brand guide, a template, a price list) and, in some tools, small scripts.
Think of it as the difference between explaining a task to a new colleague every single time and handing them a one-page checklist they keep in a drawer. The assistant reads the short description of every skill you have switched on, and only opens the full checklist when your request matches. Anthropic calls this progressive disclosure: Claude picks the relevant skills and loads only what the task needs, so a library of skills does not clutter every conversation.
In late 2026 all three big assistants use the word. Anthropic calls them Agent Skills in Claude. OpenAI's ChatGPT has skills that live inside plugins, which are replacing custom GPTs. Google's Gemini has skills, which are replacing Gems.
Skills in Claude, ChatGPT and Gemini right now
| Claude (Anthropic) | ChatGPT (OpenAI) | Gemini (Google) | |
|---|---|---|---|
| Which plans | Free, Pro, Max, Ultra, Team and Enterprise, with code execution switched on | Pricing page lists skills on Free, Go, Plus and Pro; creating and sharing plugins on Go, Plus and Pro, not Free | No Google AI subscription needed; personal Google Account, 18 or over, Keep Activity on |
| Where to find them | Customize, then Skills | Plugins in the sidebar | Customize, then Skills (click More first if you do not see Customize) |
| How to make one | Upload a ZIP: Customize, Skills, +, Create skill, Upload a skill | Install Plugin Creator, then chat with @plugin-creator | Create, then Create manually, Create with Gemini or Upload |
| How it runs | Automatically when relevant, or name it in your request | Automatically when relevant, or @ mention, + menu or Plugins in the composer | Automatically when relevant, or type / (or @) and pick it |
| What it replaces | Nothing; sits alongside Projects | Custom GPTs, retiring 11 December 2026 | Gems, read-only from 17 November 2026 |
Claude. Anthropic's help centre says skills are available on the Free, Pro, Max, Ultra, Team and Enterprise plans and in Claude Code. They need code execution: on individual plans go to Settings, then Capabilities, and switch on Code execution and file creation (called Create and edit files in the updated layout). Then open Customize, then Skills, to turn individual skills on or off. Anthropic ships its own skills for Excel, Word, PowerPoint and PDF files. A custom skill is a folder with a skill file whose name can be up to 64 characters and whose description is limited to 200 characters. On Team and Enterprise plans you can share a skill with colleagues or use Publish to org.
ChatGPT. In ChatGPT a skill is one part of a plugin. OpenAI's help centre describes a plugin as a package that can include skills (instructions and workflow guidance), connected apps such as Slack, or both. You browse them under Plugins in the sidebar on web, desktop or mobile. To build one, install Plugin Creator from the plugin directory and start a chat with @plugin-creator, or select Add (+) on the Plugins page. OpenAI's developer documentation shows each skill living in its own folder as a SKILL.md file with a name and a description. Custom GPTs retire on 11 December 2026 (11 February 2027 for FedRAMP workspaces and Enterprise workspaces with an approved deferral). When a GPT is migrated, its instructions become a skill inside the new plugin; the full story is in what is a custom GPT.
Gemini. Google's help centre says skills work without a paid subscription for people aged 18 or over who are signed in with Keep Activity on, on the web, the mobile app and the Mac app. You can ask Gemini in a chat to make one, use a template under Recommended, or upload a SKILL.md file (or a folder or .zip containing one) up to 100 MB. On personal accounts, Gems become read-only on 17 November 2026, are converted to skills automatically and are removed on 17 December 2026. Workspace business accounts follow in March 2027 and education accounts in June 2027. Only 100 skills can be active at a time, and Canvas, Deep research, Create video, Create music and Guided learning do not work with skills yet.
Why AI skills matter at work
Most of the value people get from AI at work comes from recurring tasks: the weekly status update, the client follow-up email, the meeting notes in the house format, the first pass at a contract summary. Without a skill you either retype the same long prompt every time or accept generic output. A skill fixes both problems once.
- Consistency. Everyone who uses the skill gets the same structure, tone and checks, which matters for anything a client or manager will read.
- Less prompting. Because skills can load automatically, you can simply say "write up today's call" and the assistant applies your format.
- Shared know-how. A skill written by your best performer becomes something the whole team can use. Claude Team and Enterprise let you share a skill or publish it to the whole organisation, and ChatGPT Business and Enterprise workspaces can share plugins with colleagues.
- A deadline. If your team relies on custom GPTs or Gems, the switch to skills is not optional. The dates above are when the old versions stop working.
The honest catch: automatic loading depends on the description. OpenAI warns that an installed plugin will not necessarily run on every request, and Anthropic's advice is to revise a skill's description if Claude does not use it when expected. Budget ten minutes of testing for every skill you rely on.
An example you can try in 15 minutes
Pick a task you do every week. We will use a weekly project update, because it has a clear input (notes, messages, a task list) and a clear output (a short email with fixed sections).
- Paste the first prompt below into Claude, ChatGPT or Gemini and answer its questions. It will write the skill for you: a name, a one-sentence description and step-by-step instructions.
- Check the description. It should say when to use the skill in words you would actually type, for example "Use when the user asks for a weekly project update or status report". Keep it under 200 characters so it also fits Claude's limit.
- Save it. In Gemini, open Customize, then Skills, then Create and Create manually, and paste the name, description and instructions. In ChatGPT, chat with @plugin-creator and ask for a plugin containing this skill. In Claude, save the text as a skill file in a folder, zip the folder and upload it under Customize, then Skills.
- Test it twice: once by naming the skill (or picking it with / or @), and once by just describing the task. If it does not load the second time, make the description more specific.
- Run it on last week's real notes and compare the result with what you sent. Fix one instruction at a time.
Skills compared with related terms
- Prompt: a one-off request. A skill is a prompt you have tested, written down and made reusable.
- System prompt: instructions that apply to a whole conversation. Anthropic's help centre makes the same contrast for Claude's custom instructions, which apply broadly, while skills load only when relevant.
- Custom GPT and Gems: the older, always-on assistants for one job. Skills are their replacement in ChatGPT and Gemini.
- MCP: a way to connect an assistant to outside tools and data. Anthropic describes the split neatly: MCP provides the connection, a skill provides the know-how for using it. They work together.
- AI agent: an assistant that carries out multi-step work. Skills are how you teach an agent your procedures.
- Projects: in Claude, a Project's knowledge is always loaded in its chats, whereas a skill is picked up only when needed and works across all your chats. See setting up Claude Projects.
Common misconceptions about AI skills
- "A skill is a trained or fine-tuned model." It is not. The model stays the same; a skill is text (and sometimes files and scripts) the assistant reads at the right moment. That is much closer to a saved prompt than to fine-tuning.
- "You need to code to make one." No. A simple skill is plain Markdown, and both ChatGPT and Gemini can write it for you in a chat. Scripts are optional.
- "It will run every time." Only if the description matches the request. Name the skill when the result really matters.
- "A skill moves to any assistant unchanged." Anthropic's help centre points to the Agent Skills specification, published as an open standard at agentskills.io, and the official ChatGPT and Gemini pages also use a SKILL.md file with a name and description. But details differ (Gemini wants a lowercase, hyphenated name and blocks scripts that use the internet; Claude caps descriptions at 200 characters), so test a skill in each tool before relying on it.
- "Skills from the internet are safe to install." Anthropic's own advice is to review any skill you download before enabling it and never to put passwords or API keys inside one. A skill with scripts can do more than a prompt can; treat it like software. Our guide to using AI at work safely covers the basics.
To see which assistant suits your team's skills best, read our guides to Claude, ChatGPT and Gemini, or compare them side by side in ChatGPT vs Claude.
Prompts to copy
Turn a weekly task into a skill
I want to turn this recurring task into a reusable AI skill: [describe the task, for example my weekly project update email]. Ask me up to five questions about the inputs, the output format, the tone, who reads it and common mistakes. Then write the skill with: a lowercase hyphenated name, a description under 200 characters that says exactly when to use it, step-by-step instructions, the output format, and three rules it must never break.
You get: A ready-to-save skill for Claude, ChatGPT or Gemini
Sharpen a skill that is not loading
Here is my skill's name, description and instructions: [paste]. It does not load when I type requests like [paste two or three real requests]. Rewrite the description so it matches how I actually ask, keep it under 200 characters, and point out any instructions that are vague or contradictory.
You get: A better description and a list of fixes
Test a skill against real work
Use my [skill name] skill on the notes below, then check your own output against the skill's rules and list any rule you did not follow. Notes: [paste last week's real input].
You get: A draft plus a self-check you can compare with your own version