To add and manage a large number of users at once, you can use the Google Apps Provisioning API. This allows you to integrate Google Apps with your existing corporate directory and identity management systems, such as LDAP (for example, Microsoft Active Directory).
We recommend this method for large enterprises and schools; note that it requires in-house programming or working with a Google Apps Solutions Provider.
We also have a Directory Sync tool you can use for managing users, groups and permissions. We don't recommend using this as a provisioning tool. See the next step for more information.
To start, you must first enable access to the provisioning API for your domain (go to User accounts > Settings in your Google Apps control panel).
To implement the API, we recommend reviewing the following resources:
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