What Is a Claude Extension? (And How It Reads Your Texts)

A Claude extension is a small file you install in the Claude desktop app. It lets Claude reach things on your computer, like your texts, WhatsApp and Notes. Here is what one does, how it differs from a plugin, and what it looks like in real use, with a video walkthrough.

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What is a Claude extension?

A Claude extension is a small program that runs on your own computer and gives Claude a new set of tools. It works much like an extension in your web browser: you install it once, and Claude can do something it could not do before.

That matters because connectors only reach online services like Gmail. A lot of what needs you never lives there. Your texts, your WhatsApp messages and your Notes app all sit on your Mac. An extension is how Claude gets to them.

Under the hood, an extension is a local MCP server packaged as one file ending in .mcpb. You do not need to know that to use one.

How to install a Claude extension

1. Open the Claude desktop app. Extensions run on your computer, so they need the desktop app, not the browser.
2. Drag the file in. Drop the .mcpb file onto the Claude window. You can also double-click it.
3. Review and install. Claude shows what the extension is and what it can access. Click Install and confirm.
4. Allow access on your Mac. An extension that reads your messages also needs your Mac's permission. You grant it once in System Settings.
5. Check the tools. Open the extension in Claude's settings to see its tools listed. In the video, those tools let Claude read the apps from the opening shot.

Extension vs plugin: what is the difference?

The two get mixed up all the time, and you often want both. The short version:

• The extension gives Claude access. It opens the door to your messages and notes.
• The plugin tells Claude what to do with that access. It holds the instructions: your people, your rules and what counts as urgent.

A skill is one set of those instructions. A plugin is a package that can hold several skills and connectors, installed together. A connector links Claude to an online service. An extension does the same job for what is on your computer.

You can change a plugin whenever you like. In the video we add a new rule by typing it in plain English.

What it looks like: one page for everything

The example in the video is a daily brief. Once the extension and plugin are on, you ask Claude to run your brief, and it pulls everything together:

• One page. Everything that needs you, from email, texts, WhatsApp and Notes, sorted by what is urgent.
• Replies already written. Claude drafts a response to each message. You can change anything you want.
• You send it. Nothing goes out until you click.
• It runs on a schedule. Set it to run whenever you want, change what shows up, and connect things like Gmail and your calendar.

The names and messages in the video are made up. We would never show real ones.

What to know before you install one

• Only install extensions you trust. An extension runs on your computer, and one that reads your messages can see all of them. Check who made it first.
• Your computer needs to be on. Extensions run locally, so scheduled runs need your computer awake and Claude open. Anything that arrives while it sleeps shows up on the next run.
• Local does not mean private from Claude. The extension runs on your machine, but what it reads goes into your Claude conversation. Read how Claude handles business data before you connect anything sensitive.
• Your company may control this. On Team and Enterprise plans, admins can turn extensions off or limit which ones you can install.

Learn more about extending Claude

For the other pieces, read our guide to Claude skills, how to connect Gmail to Claude and how to schedule a task in Claude. Anthropic's post on desktop extensions covers the technical side.

Frequently asked questions

What is a Claude extension?

A Claude extension is a small file you install in the Claude desktop app. It runs on your own computer and lets Claude reach things that live there, like your texts, WhatsApp and Notes.

How do I install a Claude extension?

Open the Claude desktop app and drag the .mcpb file into the window. Review what it can access, click Install and confirm. Your Mac may also ask you to allow access.

What is the difference between a Claude extension and a plugin?

An extension gives Claude access. A plugin tells Claude what to do with that access. In our example, the extension reads your messages, and the plugin holds your people, your rules and what counts as urgent.

What is the difference between an extension and a connector?

A connector links Claude to an online service, like Gmail. An extension runs on your own computer, so it can reach apps and files that have no online connection for Claude to use.

Can Claude send messages without my approval?

Not in the setup shown in this post. Claude drafts the reply, you can change it, and nothing goes out until you click.