Claude Skills vs Projects vs Custom GPTs: What's the Difference and Which Should You Use?

Why this matters

There are now at least three ways to make an AI assistant "yours": Claude Skills, Claude Projects, and ChatGPT's Custom GPTs. They get pitched with the same words - custom instructions, reusable, tailored - and people end up building a Project when they needed a Skill, or a Custom GPT they cannot move anywhere else.

This post lays out what each one actually is, where it lives, what it is good for, and which to reach for first. The short version is that they are not competitors. Two of them are ways of organizing Claude; one is a ChatGPT-only container; and Skills are the only one of the three that works across agents.

The one-line version of each

Claude Skills are folders of instructions (SKILL.md files) that Claude loads on demand when a task matches. They teach Claude how to do a job, and they are portable: the same file works in Claude, Claude Code, ChatGPT and Codex, Cursor, and 40+ other agents.

Claude Projects are workspaces inside the Claude app with their own chat history, uploaded knowledge files, and custom instructions. They give Claude background for an initiative - a client, a product, a research topic.

Custom GPTs are ChatGPT-only assistants configured with instructions, up to 20 knowledge files, and optional API "actions." They package a persona plus knowledge into a shareable chatbot.

Claude Skills vs Projects vs Custom GPTs: side by side

	Claude Skills	Claude Projects	Custom GPTs
What it holds	Procedures: step-by-step instructions, examples, optional scripts and references	Knowledge files, project instructions, chat history	Instructions, up to 20 knowledge files (512 MB each), API actions
Best at	Doing a specific task the same way every time	Keeping context for an ongoing initiative	Packaging a branded assistant for others to use
When it loads	Only when a task matches the skill's description	Every chat inside that Project	Every chat with that GPT
Works in	Claude, Claude Code, ChatGPT/Codex, Cursor, Copilot, Gemini CLI, 40+ agents	The Claude app only	ChatGPT only
Portable / open standard	Yes - SKILL.md at agentskills.io	No	No
Who can create	Anyone, on any Claude plan (upload under Customize > Skills)	Any Claude user; free accounts get up to five Projects	Business, Enterprise, and Edu workspaces only, per OpenAI's current help docs
Sharing	Copy the folder, share a repo, or publish to a marketplace	Team and Enterprise plans	Share links within workspace rules
Can combine with the others	Yes - use inside a Project or alongside MCP	Yes - Projects can use Skills	Limited to ChatGPT

What Claude Skills are for

A Skill is a procedure. Anthropic's own comparison describes Skills as "folders containing instructions, scripts, and resources that Claude discovers and loads dynamically when relevant to a task," and recommends them for "specialized, repeatable tasks - organizational workflows, domain expertise, and personal preferences that apply across multiple conversations."

The key phrase is across multiple conversations. A Skill is not tied to one workspace or one chat. If you have a way you want cold emails rewritten, meeting notes structured, or proposals drafted, that is a Skill, and it will fire in any conversation - inside a Project, outside one, or in a completely different agent.

A few examples from the AgentVolt marketplace that show the shape: Cold Email Refiner (a rewrite checklist), Meeting Notes Synthesizer (transcript to action items), Stop Slop Skill (rules for removing AI-writing tells). None of them need to know anything about your project. They know how to do one job.

Our guide to agent skills covers the format in depth.

What Claude Projects are for

A Project is a room. Anthropic describes Projects as "self-contained workspaces with their own chat histories and knowledge bases." You upload the documents that matter for an initiative - the brief, the brand guide, the last three reports - set project-level instructions, and every chat inside the Project starts with that context loaded. When the knowledge base gets large, Claude switches to retrieval mode to extend capacity up to ten times.

Projects are for what Claude should know, not how Claude should work. A Project for a client holds the client's material; it does not hold your proposal-writing procedure. That procedure is a Skill, and it works in every client's Project.

Projects are available on every Claude plan (free accounts get up to five); sharing them with teammates requires Team or Enterprise.

What Custom GPTs are for

A Custom GPT is a packaged assistant. You give it instructions, upload knowledge files, optionally connect it to an API through actions, and publish it so other people can chat with it. It is the closest thing to "build a chatbot for my audience" without writing code, and for that purpose it is still good.

Two things changed in 2026 that matter for the comparison. First, OpenAI's help documentation now states that only Business, Enterprise, and Edu workspaces can create and publish GPTs; personal Free, Go, Plus, and Pro accounts can use existing GPTs but not build new ones. Second, OpenAI's own Codex adopted the SKILL.md standard, which means the portable way to give ChatGPT's coding agent a procedure is now a Skill, not a GPT.

A Custom GPT lives inside ChatGPT. If you move to Claude, Cursor, or Gemini, it stays behind.

Which one should you use?

Ask what the thing is.

If it is a way of doing a task - a checklist, a rewrite procedure, a format you want every time - it is a Skill. Build it once; it works everywhere.

If it is a body of material about one initiative - a client, a product launch, a thesis - it is a Project. Put the documents there and let Claude reference them.

If it is a chatbot for other people to talk to inside ChatGPT, and you have a workspace plan, it is a Custom GPT.

Most real setups use the first two together: a Project per client with the client's files, and a handful of Skills that run the same way in every Project. That combination is what people usually mean when they say Claude "knows how they work."

Can you move between them?

Skills are the only one of the three that travels. A SKILL.md you write for Claude works unchanged in Codex, Cursor, and the rest, and our install guide has the path for each. A Project's knowledge files can be re-uploaded elsewhere, but the Project itself does not export. A Custom GPT's instructions can be copied out by hand and rewritten as a Skill, which is the migration path many teams are taking now that GPT creation is restricted to workspace plans.

If you have a Custom GPT you rely on, turning its instructions into a Skill takes about twenty minutes. Our SKILL.md guide has the template.

Frequently asked questions

Are Claude Skills the same as Custom GPTs?

No. A Custom GPT is a ChatGPT-only assistant with instructions and knowledge files. A Skill is a portable procedure file that loads on demand and works in Claude, ChatGPT's Codex, Cursor, and 40+ other agents. Skills are closer to a reusable playbook than a chatbot.

Can I use Skills inside a Claude Project?

Yes. Skills apply across your whole account, so any Skill you have installed will fire inside a Project when a task matches. That is the recommended setup: Project for context, Skills for procedures.

Do I need a paid plan for Claude Skills?

No. Skills are available on Free, Pro, Max, Team, and Enterprise plans. Upload a skill under Customize > Skills after enabling code execution under Settings > Capabilities.

Can I still create a Custom GPT on ChatGPT Plus?

According to OpenAI's help documentation as of this writing, creating and publishing GPTs is available in Business, Enterprise, and Edu workspaces; personal plans can use existing GPTs. Check OpenAI's current docs, since this has changed before.

The takeaway

Projects hold what Claude should know. Skills hold how Claude should work. Custom GPTs package both into a ChatGPT-only assistant. If you want something you can build once and use everywhere, it is a Skill.

Browse ready-made Skills on AgentVolt - 1,000+ reviewed, security-scanned procedures for sales, content, productivity, finance, and development, installable in Claude or any agent on the standard.