How to add a custom connector to Claude

Short answer

Open Customize › Connectors on claude.ai, click Add custom connector, paste the server's URL and click Add. Then click Connect and sign in. It takes two minutes. Custom connectors work on Free, Pro, Max, Team and Enterprise, but Free allows only one. On Team and Enterprise, an Owner adds the connector for the organization first, and each member then connects their own account.

What a custom connector is

A connector lets Claude use another app. Under the hood, each one is a remote MCP server: a small web service that offers Claude a set of tools, such as "search email" or "create task", over the internet. MCP (Model Context Protocol) is the open standard they speak.

• Directory connectors are listed in the Connectors Directory. You add them with one click.
• Custom connectors are any remote MCP server you add by URL. Claude labels them Custom, and Anthropic hasn't reviewed them.
• Desktop extensions run a server on your own computer, inside Claude Desktop. They're a different thing, installed under Settings › Extensions.

Both kinds of web connector run on the same infrastructure and work in claude.ai, Claude Desktop, Cowork and the mobile apps. For Claude Code, you add servers from the terminal instead. See Claude Code MCP servers.

What you need

• The server's URL. It must be HTTPS and reachable from the public internet. Claude connects from Anthropic's cloud, not from your computer, so localhost and servers behind a VPN won't work.
• A plan. Any plan works. Free allows one custom connector.
• The right role on Team and Enterprise. Owners and Primary Owners can add connectors. On Enterprise, so can members whose custom role includes managing the organization's libraries. Everyone else asks an Owner.
• The web or desktop app. Add the connector there. Once added, it shows up in the mobile apps too.

Add a custom connector on Free, Pro or Max

We'll use Upsy as the example. It's one connector that holds your email, calendar, files, memory and a cloud browser.

1. Get the URL. For Upsy, sign up at upsy.ai, click Add assistant, pick Claude under Which assistant?, and copy the address:

   https://upsy.ai/connect
   

2. In Claude, go to Customize › Connectors.

3. Click Add custom connector. On some accounts it sits behind a + Add button.

4. Enter a name (this is what you'll see in the list) and paste the URL.

5. Claude may show authentication settings. The layout varies by account. For a server that uses OAuth, like Upsy, keep the defaults:

   • Authentication: sign in now, or when needed.
   • OAuth client: "Use Claude's published identity" is Anthropic's recommendation. Upsy also works with "Register automatically".
   • Leave any client ID, secret and request headers empty.

6. Click Add.

7. Click Connect next to the new connector. A sign-in page opens. For Upsy, sign in, tick what Claude may use, choose Read-only or full access for each app, and click Allow.

You'll come back to Claude with the connector connected.

Add it for a Team or Enterprise organization

The Owner does this once:

1. Go to Organization settings › Connectors.
2. Click Add, then Custom. If Claude asks for the type, choose Web.
3. Enter the URL, and OAuth credentials only if the server needs them. Upsy doesn't.
4. Click Add.

Each member then opens Customize › Connectors, finds the connector with the Custom label, and clicks Connect to sign in with their own account. Owners can also set each tool to Always allow, Needs approval or Blocked for everyone, under the connector's Tool permissions.

Use it in a chat

• Click + in the chat box, hover over Connectors, and check the connector is on. You can turn each connector on or off per chat.
• If you have many connectors, Tool access in the same menu can load them On demand instead of Auto.
• When Claude asks to use a tool, read the request. Choose Always allow only for tools and servers you trust.

Check that it works

Send this:

What can you do with Upsy? List its tools.

Claude should list the tools you allowed, grouped by app, such as Gmail search and send, calendar events, files and the browser. Anything you didn't allow won't appear at all.

Edit or remove a connector

Go to Customize › Connectors, then click Remove or the three-dot menu. You can change a connector's name or URL. You can't change its authentication settings: remove it and add it again, then reconnect.

Troubleshooting: Claude connectors not working

Anthropic's troubleshooting page lists three errors.

"Couldn't reach the MCP server"

Claude couldn't finish the first handshake. Check the URL is exact, with no typo or extra path, and that it's public: not localhost, a home network or a VPN. If the server is fine, a firewall may be blocking Anthropic. That's for the server's owner to fix.

"Authorization with the MCP server failed"

The sign-in started but didn't finish. Allow pop-ups and redirects for claude.ai, then click Connect again. If you closed the sign-in page early, start over. With Upsy, make sure you clicked Allow, not Deny.

"Unexpected error while invoking tool"

The connector is connected, but one tool call failed on the server's side. Claude shows the tool's name. Ask Claude what the tool said. With Upsy, the most common reasons are an app that needs reconnecting in Upsy, or one this assistant isn't allowed to use, and Upsy's message says which.

There's no Add custom connector button

On Team and Enterprise, only Owners can add one, so ask yours. On Free, you may have used your one custom connector already. Remove it, or use one connector that covers several apps.

It's connected, but Claude doesn't use it

Check it's on for this chat under + › Connectors. Then name it in your prompt: "Use Upsy to check my calendar."

Reporting a failure

When a connection fails, the error and the page address include a reference that starts with ofid_. Copy it into any support request to Anthropic or the server's owner, soon after the failure.

Security and privacy

Anthropic is direct about custom connectors. They connect Claude to services it hasn't verified, and Claude can read and change data there. Connect only servers you trust. Check the permissions you're asked for, and watch for tools that start behaving differently. A malicious server could also hide instructions in its replies.

If Upsy is your custom connector:

• Claude never gets your app passwords or tokens. It calls Upsy's tools, and Upsy calls the app.
• You set each app and account to No access, Read-only, Full access, or only the actions you pick.
• Every action is in Upsy's History. Upsy emails you if Claude deletes, sends or reads a lot at once.
• Upsy has no approval prompt of its own. Claude's prompts are the check before each action.
• One switch on the Assistants page turns Claude off.

FAQ

How do I add a custom connector to Claude?

Go to Customize › Connectors, click Add custom connector, paste the server URL and click Add. Then click Connect and sign in.

How many custom connectors can I add on the Free plan?

One. Anthropic states that limit only for Free. A connector like Upsy, which holds many apps, counts as one.

What's the difference between Claude connectors and MCP?

MCP is the open standard. A connector is Claude's name for an MCP server you've added, whether from the directory or by URL.

Can I add a custom connector on the Claude mobile app?

Add it on claude.ai or in Claude Desktop. Once added, you can use it in the iOS and Android apps.

Can I use an API key instead of OAuth?

Some organizations can enter an API key under Request headers in the add dialog. Anthropic says the feature is in beta for a limited set of organizations. Upsy signs in with OAuth and needs no key.

Is a custom connector the same in Claude Cowork?

Yes. Custom connectors work in Cowork, Claude Desktop and claude.ai alike.