<a id="mailchimp"></a>

# MailChimp

<a id="backend-class"></a>

## Backend class

For Django, add this class path to `AUTHENTICATION_BACKENDS`. For other
integrations, use the same class path in the framework-specific backend
setting.

| Backend name   | Class path                                       |
|----------------|--------------------------------------------------|
| `mailchimp`    | `social_core.backends.mailchimp.MailChimpOAuth2` |

MailChimp uses OAuth v2 for Authentication, check the [official docs](https://apidocs.mailchimp.com/oauth2/).

- Create an app by filling out the form here: [Add App](https://admin.mailchimp.com/account/oauth2/)
- Fill `Client ID` and `Client Secret` values in the settings:
  ```default
  SOCIAL_AUTH_MAILCHIMP_KEY = '<App UID>'
  SOCIAL_AUTH_MAILCHIMP_SECRET = '<App secret>'
  ```
- Add the backend to the `AUTHENTICATION_BACKENDS` setting:
  ```default
  AUTHENTICATION_BACKENDS = (
      ...
      'social_core.backends.mailchimp.MailChimpOAuth2',
      ...
  )
  ```
- Then you can start using `{% url social_core:begin 'mailchimp' %}` in
  your templates

<a id="identity-and-upgrade-behavior"></a>

## Identity and upgrade behavior

The backend identifies a connection by the Mailchimp account’s `user_id`
and the authorizing person’s `login.login_id`. Different people with access
to one Mailchimp account therefore have separate local identities. One person
connecting multiple Mailchimp accounts also has a separate association for
each account. The metadata response must contain both identifiers.

Older versions associated users by `user_id` alone. On the next sign-in,
an older association is migrated only if its saved `login.login_id` matches
the person signing in. If the saved login differs, that person receives a
separate local association. If the saved login identifier is missing, sign-in
stops and the application must use independently verified account recovery or
authenticated account linking. A saved login records the last person who
used an older association, so applications should audit accounts that may
already have been shared before upgrading.

Mailchimp accepts only `mailchimp_identity` as its configured `ID_KEY`.
Before upgrading, remove any `SOCIAL_AUTH_MAILCHIMP_ID_KEY` or global
`SOCIAL_AUTH_ID_KEY` value that selects `user_id` or another identifier.
The backend rejects those settings because they can bind different people to
one local account.