Connection Guide

Connection URI

The connection URI is the set of instructions that the driver uses to connect to a MongoDB deployment. It tells the driver how to connect to MongoDB and how to behave while connected. The following example shows each part of the connection URI:

In this example, we connect to an Atlas MongoDB deployment that has a DNS SRV record. For more details, see the DNS Seed List Connection Format documentation. This format offers flexibility in deployment and the ability to change the servers in rotation without reconfiguring clients.

If you are connecting to an instance or replica set that does not have a DNS SRV address, you must use mongodb for the protocol, which specifies the Standard Connection String Format.

After the protocol, the next part of the connection string contains credentials if you are using password-based authentication. Replace the value of user with your username and pass with your password. If you are using an authentication mechanism that does not require a username and password, omit this part of the connection URI.

The next part of the connection string specifies the hostname or IP address of your MongoDB instance, followed by the port number. In the example above, we use sample.host as the hostname and 27017 as the port. Replace these values to point to your MongoDB instance.

The last part of the connection string contains connection and authentication options as parameters. In the example above, we set two connection options: maxPoolSize=20 and w=majority. For more information on connection options, skip to the Connection Options section.

Atlas Connection Example

You must create a client to connect to a MongoDB deployment on Atlas. To create a client, construct an instance of MongoClient, passing in your URI and a MongoClientOptions object.

Use the serverApi option in your MongoClientOptions object to enable the Stable API feature, which forces the server to run operations with behavior compatible with the specified API version.

The following code shows how you can specify the connection string and the Stable API client option when connecting to a MongoDB deployment on Atlas and verify that the connection is successful:

const { MongoClient, ServerApiVersion } = require("mongodb");
// Replace the placeholder with your Atlas connection string
const uri = "<connection string>";
// Create a MongoClient with a MongoClientOptions object to set the Stable API version
const client = new MongoClient(uri,  {
        serverApi: {
            version: ServerApiVersion.v1,
            strict: true,
            deprecationErrors: true,
        }
    }
);
async function run() {
  try {
    // Connect the client to the server (optional starting in v4.7)
    await client.connect();
    // Send a ping to confirm a successful connection
    await client.db("admin").command({ ping: 1 });
    console.log("Pinged your deployment. You successfully connected to MongoDB!");
  } finally {
    // Ensures that the client will close when you finish/error
    await client.close();
  }
}
run().catch(console.dir);

To learn more about the Stable API feature, see the Stable API page.

Other Ways to Connect to MongoDB

If you are connecting to a single MongoDB Server instance or replica set that is not hosted on Atlas, see the following sections to find out how to connect.

mongodb://localhost:<port>

mongodb://host1:27017,host2:27017,host3:27017/?replicaSet=myRs