What is the difference between Claude Skills, ChatGPT plugins and Gemini skills?

All three are ways to save reusable instructions so you do not retype them. Claude Skills are folders with a SKILL.md file (instructions plus metadata) and optional scripts, templates and reference files, loaded on demand across Claude.ai, Claude Code and the Claude API, and packaged into Agent Plugins. ChatGPT plugins are OpenAI's replacement for custom GPTs: a plugin bundles skills (the GPT's instructions), reference files and connected apps, and follows the vendor-neutral Agent Plugins standard so it also runs in Codex, Cursor and Copilot. Gemini skills are reusable custom instructions invoked with / (soon @) in any Gemini chat, applied automatically when relevant and stackable; they replace Gems starting November 17, 2026.

Are custom GPTs going away?

Yes. OpenAI announced on September 11, 2026 that custom GPTs will retire on December 11, 2026 (February 11, 2027 for Enterprise workspaces with an approved deferral). Since September 16, 2026 new GPTs can only be created in Business, Enterprise or Edu workspaces. Creators migrate via My GPTs → Migrate to plugin: instructions become a skill, knowledge files become reference files, connected apps become apps. Custom actions do not transfer and must be rebuilt (often as an MCP server), the selected model does not carry over, and existing conversations do not move.

When do Gemini Gems become skills?

Gems begin migrating to skills on November 17, 2026 for personal Google accounts, in March 2027 for Workspace business, enterprise and non-profit accounts, and in June 2027 for Workspace education accounts. Google migrates them automatically (with supported files); you can recreate a Gem as a skill earlier from Settings → Skills → Create manually. Opal and Gems by Google Labs also shut down in November. Skills do not yet work with Canvas, Deep Research, guided learning, or the video and music creation tools that Gems could default to.

Which one should I use in 2026?

Use the one your daily assistant uses, but write the instructions in the Claude Skills / Agent Skills format: a SKILL.md with a clear 'when to use' description and bundled reference files. That format is what Claude loads natively, what ChatGPT plugins wrap (GPT instructions become a skill inside the plugin), and what the Agent Plugins standard carries across Cursor, Copilot, Codex, VS Code and Kiro. Gemini skills are the least portable: personal accounts only for now, no bundled scripts, and a 100 MB file limit.

Quick Answer

Claude Skills vs ChatGPT Plugins vs Gemini Skills (2026)

Published: September 29, 2026

The short answer

In 2026 the three big assistants converged on the same idea — a reusable, on-demand instruction package called a “skill” — and two of them are killing their older formats to get there. Claude Skills (a SKILL.md folder with optional scripts and files) are the reference design and run across Claude.ai, Claude Code and the API. OpenAI is retiring custom GPTs on December 11, 2026 and migrating them into plugins, where the GPT’s instructions become a skill. Google is retiring Gemini Gems starting November 17, 2026 in favor of skills you invoke with / in any chat. If you write your instructions once in the skills format, they travel; if you build in Gems or GPTs today, you are building on a deadline.

Side by side

	Claude Skills	ChatGPT plugins (ex custom GPTs)	Gemini skills (ex Gems)
Unit	Folder with `SKILL.md` (instructions + metadata) plus optional scripts, templates, reference docs	Plugin = skills + reference files + apps (connected services), `plugin.json` manifest	Reusable custom instructions, optional reference files (≤100 MB)
Where it runs	Claude.ai, Claude Code, Claude API, and any Agent Plugins client	ChatGPT, Codex; and via the Agent Plugins standard Cursor, GitHub Copilot, VS Code, Kiro	Gemini app chat (personal accounts; work/school “soon”); Gemini CLI / Vertex have separate developer Agent Skills
Invocation	Automatic: model reads name + description, loads the full skill only when relevant	Plugin selects the right skill; installed per user or workspace	`/skill-name` (soon `@`); also auto-applied when Gemini judges it relevant; stackable
Code execution	Yes — bundled Python scripts run when instructions call for them	Apps and MCP servers; custom GPT “actions” must be rebuilt	No
Portability	High: Agent Skills is the format inside the Agent Plugins standard	High for plugins; zero for legacy GPTs after Dec 11, 2026	Low: Gemini app only; Google lists importing skills from other platforms as a FAQ but the instructions are manual copy-paste
Sharing	Files in a repo; org-managed in Claude Code	Plugin starts private after migration; workspace publishing	Gems were link-shareable; skills live in any chat, no dedicated page
Sunset	—	Custom GPTs retire Dec 11, 2026 (Feb 11, 2027 with Enterprise deferral)	Gems → skills Nov 17, 2026 (personal), Mar 2027 (Workspace business), Jun 2027 (education)
Not supported	—	Custom actions, selected model, old conversations do not migrate	Canvas, Deep Research, guided learning, Create video/music

Format background: Agent Plugins vs MCP vs Agent Skills and what is the OpenAI Agent Plugins standard. The April 2026 version of this comparison, written when Gems and custom GPTs were still the plan, is at Claude Skills vs custom GPTs vs Gemini Gems.

Claude Skills: the reference design

A Claude Skill is a directory. SKILL.md carries frontmatter (name, description) and the procedure; the folder can also hold scripts, templates and reference files. The design principle is progressive disclosure: Claude pre-loads only each skill’s name and description, decides relevance from that, reads the full SKILL.md only on a match, and opens bundled files only when the instructions call for them. That keeps dozens of skills resident without flooding the context window.

Skills work in Claude.ai, in Claude Code (where the bundled Claude API skill will, for example, migrate a codebase to Sonnet 5.5 with /claude-api migrate), and through the API. Because the Agent Plugins standard (August 6, 2026; OpenAI, Amazon, Cursor, Microsoft, Vercel, with Google as a core maintainer) adopted Agent Skills as its expertise layer, a well-written SKILL.md is the most portable artifact in this space. Security notes for anything that bundles executable scripts: how to secure AI coding-agent plugins and skills.

ChatGPT plugins: what happens to your custom GPT

OpenAI’s timeline, from its retirement FAQ:

September 11, 2026: retirement announced.
September 16, 2026: creating new custom GPTs restricted to Business, Enterprise and Edu workspaces.
December 11, 2026: custom GPTs and their GPT pages become inaccessible. Enterprise workspaces with an approved deferral get until February 11, 2027.

Migration is per GPT: My GPTs → Migrate to plugin. The latest published version migrates (drafts do not); its instructions become a skill inside the plugin, knowledge files become reference files, connected apps become apps. The plugin starts private and is not auto-installed for other users. Three things do not carry over: custom actions (rebuild as an available app or a custom MCP server), the GPT’s selected model (Enterprise defaults apply), and existing conversations. After migration the original GPT becomes read-only until retirement.

If you use someone else’s GPT, watch its notice for the creator’s replacement; permission to use a GPT does not include permission to migrate it. Plugins run in ChatGPT and Codex and, through the standard, in Cursor, Copilot, VS Code and Kiro — which is the upgrade: a GPT was ChatGPT-only, a plugin is not. Related: ChatGPT voice, plugins and GPT-6 switching.

Gemini skills: what happens to your Gems

Google’s help center and the Gems manager notice (“Gems will become skills starting Nov 17, 2026”):

Personal Google accounts: migration begins November 17, 2026. Workspace business, enterprise, non-profit: March 2027. Workspace education: June 2027.
Gems are migrated automatically, with supported files. You can recreate one earlier: open the Gem, download its knowledge files, then Settings → Skills → Create manually, paste name, description and instructions, and upload files by downloading the skill and re-uploading it with them.
Opal (Google Labs’ mini-app builder) and Gems by Google Labs shut down at the same time in November.

What you gain: / invocation from any chat (@ soon), automatic application when Gemini recognizes a match, and stacking several skills in one conversation — Gems required a side-panel detour and could not be combined. What you lose: Gems could set a default tool (Create image, Canvas) and be shared by link; skills do not yet work with Canvas, Deep Research, guided learning, or video and music creation, and there is no dedicated page listing the chats that used a skill. Skills are available now to signed-in adults on personal accounts (AI Pro and Ultra subscribers can also build them in the Gemini Spark tab); work and school accounts follow. Developers building agents on Gemini CLI or Vertex AI use a separate, more capable “Agent Skills” system.

How to write a skill that survives all three

Lead with the trigger. The description must say when to use it — that is what Claude and Gemini read to decide. Google’s own best practice: “describe specific situations when Gemini should use the skill automatically.”
Keep the body to the procedure. Unique guidelines only; no restating defaults. Put long references in bundled files (Claude) or reference files (plugins, Gemini ≤100 MB).
Include examples of expected output. All three vendors recommend it.
Keep integrations outside the skill. Tool connections belong in MCP servers (Claude, plugins) or connected apps (Gemini); GPT custom actions did not survive migration for exactly this reason.
Store the source in a repo as a SKILL.md folder. From there: use directly in Claude, wrap in a plugin.json for ChatGPT/Codex/Cursor/Copilot, and paste the instructions into a Gemini skill.

Decision rule

Daily driver is Claude or Claude Code: Claude Skills, in a repo, optionally packaged as an Agent Plugin.
Daily driver is ChatGPT and you own custom GPTs: migrate to plugins now; rebuild custom actions as MCP before December 11, 2026.
Daily driver is the Gemini app: recreate important Gems as skills before November 17, 2026 rather than waiting for auto-migration, and check the missing-tools list.
You ship one extension to many clients: author Agent Skills, package as an Agent Plugin; treat Gemini skills as a manual export.

Last verified: September 29, 2026.