> For clean Markdown of any page, append .md to the page URL.
> For a complete documentation index, see https://mailchimp.com/developer/marketing/api-concepts/authentication/api-keys/llms.txt.
> For AI client integration (Claude Code, Cursor, etc.), connect to the MCP server at https://mailchimp.com/_mcp/server.

# API keys

> How Mailchimp API keys behave, and where they can and cannot be used.

An [API key](https://mailchimp.com/help/about-api-keys/) authenticates requests
against the account it was created in. It's the right credential when your
application works with your own Mailchimp data. To create one, see
[Generate your API key](/marketing/build/get-started/generate-your-api-key).

## What a key grants

A key carries full access to the account it belongs to. There is no way to
issue a read-only key or restrict one to particular endpoints, so treat a key
the way you'd treat a password.

Keys don't expire. A key stays valid until you delete it, or until the user who
created it is removed from the account; see
[User access and revocation](/marketing/api-concepts/authentication#user-access-and-revocation).

## Where keys can't be used

Because a key grants full account access, two environments are ruled out:

* **Browsers.** Mailchimp does not support client-side calls to the Marketing
  API using CORS requests. A key in front-end code is readable by anyone who
  loads the page.
* **Mobile apps.** A key shipped inside a distributed binary can be extracted
  from it. For iOS and Android, use the
  [Mobile SDK](/marketing/build/start-developing/mobile-sdk), which is built
  against a mobile-focused subset of the API.

Both cases have the same shape: the credential ends up somewhere you don't
control. Keep keys on a server you own.

> Find all the Mailchimp API documentation and tools developers need to send marketing and transactional emails.