Docs Menu

Docs HomeDevelop ApplicationsMongoDB Manual


On this page

  • User Management Interface
  • Authentication Database
  • Authenticate a User
  • Centralized User Data
  • Sharded Cluster Users
  • Localhost Exception

To authenticate a client in MongoDB, you must add a corresponding user to MongoDB.

To add a user, MongoDB provides the db.createUser() method. When adding a user, you can assign roles to the user in order to grant privileges.


The first user created in the database should be a user administrator who has the privileges to manage other users. See Enable Access Control.

You can also update existing users, such as to change password and grant or revoke roles. For a full list of user management methods, see User Management.

A user is uniquely identified by the user's name and associated authentication database. Starting in MongoDB 4.0.9, a users managed by MongoDB are assigned a unique userId. [1]


See also:

When adding a user, you create the user in a specific database. This database is the authentication database for the user.

A user can have privileges across different databases; that is, a user's privileges are not limited to their authentication database. By assigning to the user roles in other databases, a user created in one database can have permissions to act on other databases. For more information on roles, see Role-Based Access Control.

The user's name and authentication database serve as a unique identifier for that user. [1] That is, if two users have the same name but are created in different databases, they are two separate users. If you intend to have a single user with permissions on multiple databases, create a single user with roles in the applicable databases instead of creating the user multiple times in different databases.

[1](1, 2) Starting in version 4.0.9, MongoDB associates a user with a unique userId upon creation in MongoDB.LDAP managed users created on the LDAP server do not have an associated document in the system.users collection, and hence, do not have a userId field associated with them.

To authenticate as a user, you must provide a username, password, and the authentication database associated with that user.

To authenticate using the mongo shell, either:

  • Use the mongo command-line authentication options (--username, --password, and --authenticationDatabase) when connecting to the mongod or mongos instance, or

  • Connect first to the mongod or mongos instance, and then run the authenticate command or the db.auth() method against the authentication database.


    Authenticating multiple times as different users does not drop the credentials of previously-authenticated users. This may lead to a connection having more permissions than intended by the user, and causes operations within a logical session to raise an error.

For examples of authenticating using a MongoDB driver, see the driver documentation.

For users created in MongoDB, MongoDB stores all user information, including name, password, and the user's authentication database, in the system.users collection in the admin database.

Do not access this collection directly but instead use the user management commands.

To create users for a sharded cluster, connect to the mongos instance and add the users. Clients then authenticate these users through the mongos instances. In sharded clusters, MongoDB stores user configuration data in the admin database of the config servers.

However, some maintenance operations, such as cleanupOrphaned, compact, rs.reconfig(), require direct connections to specific shards in a sharded cluster. To perform these operations, you must connect directly to the shard and authenticate as a shard local administrative user.

To create a shard local administrative user, connect directly to the shard and create the user. MongoDB stores shard local users in the admin database of the shard itself.

These shard local users are completely independent from the users added to the sharded cluster via mongos. Shard local users are local to the shard and are inaccessible by mongos.

Direct connections to a shard should only be for shard-specific maintenance and configuration. In general, clients should connect to the sharded cluster through the mongos.

The localhost exception allows you to enable access control and then create the first user in the system. With the localhost exception, after you enable access control, connect to the localhost interface and create the first user in the admin database. The first user must have privileges to create other users, such as a user with the userAdmin or userAdminAnyDatabase role. Connections using the localhost exception only have access to create the first user on the admin database.

Changed in version 3.4: MongoDB 3.4 extended the localhost exception to permit execution of the db.createRole() method. This method allows users authorizing via LDAP to create a role inside of MongoDB that maps to a role defined in LDAP. See LDAP Authorization for more information.

The localhost exception applies only when there are no users created in the MongoDB instance.

In the case of a sharded cluster, the localhost exception applies to each shard individually as well as to the cluster as a whole. Once you create a sharded cluster and add a user administrator through the mongos instance, you must still prevent unauthorized access to the individual shards. Follow one of the following steps for each shard in your cluster:

  • Create an administrative user, or

  • Disable the localhost exception at startup. To disable the localhost exception, set the enableLocalhostAuthBypass parameter to 0.

← Authentication