Before we go into much further detail we’ll cover the concept and structure of a MongoDB connection URL.

The most basic example of this would be mongodb://localhost. This consists of the schema (mongodb:// which is required in all MongoDB connection URLs) as well as the hostname, in this case, localhost.

The hostname can be either an IP address or a full address like example.com.

Hostnames can be succeeded by a semicolon : and a port. A port is a number between 0 and 66535. By default MongoDB is hosted on 27017 which is used by default.

In the URL you can also add the username and password and authentication database.


In this example the hostname is example.com. The instance should be hosted at port 12345 and we’re authenticating at the username usern4m3 and the password p455word. The username and password should be URL percent encoded and the authentication database is admin

Last but not least we can specify multiple hosts in the case of a replica set.


In this example we’re connecting to a replica set of 3 hosts.

  • host0.example.com:12345
  • host1.example.com:54321
  • host2.example.com:27017

Query parameters

After the URL’s path (the database) you can optionally add Query parameters.

These are started with a question mark (?) and have key-value pairs. Pairs are separated by an ampersand (&). Every key-value pair has a key which is a string without &, ? or = characters (unless percent encoded) which is then followed by an equals sign (=), followed by a value. The = and value are optional for some parameters.


This URL has three keys: - ssl - authSource - authMechanism

  • ssl doesn’t have a value
  • authSource has the value admin
  • authMechanism has the value MONGODB-CR


SSL is enabled for a server by adding the query parameter key ssl.



authSource indicates that the authentication database differs from the default (admin) or the selected database in the path.

Where mongodb://mongodb.example.com:12345/myDatabase will use myDatabase for authentication and mongodb://mongodb.example.com:12345 will use admin.

mongodb://mongodb.example.com:12345/myDatabase?authSource=test will use admin for authentication. This is also useful for databases where the user logs in against admin but the path is used for selecting a database, for example, in the Database initializer.



Selects a mechanism that will be used for authentication to the MongoDB server.

MongoDB supports the following mechanisms: - SCRAM_SHA_1 - MONGODB-CR - MONGODB-X509 - GSSAP - PLAIN

MongoKitten only supports SCRAM_SHA_1 and MONGODB-CR, currently.