On this page
- Database deployment Connect button is disabled
- Connecting IP address not in IP Access List
- Authentication to the database deployment failed
- Too many open connections to your database deployment
- Degraded performance in sharded clusters during spikes in connection counts
- Attempting to connect from behind a firewall
- Database Deployment Availability
- MongoDB Compass Troubleshooting
- Connection String Issues
This page outlines common connection issues and possible resolutions.
To learn more about connecting to an Atlas cluster, see the Get Started with Atlas tutorial.
Serverless instances don't support connecting via certain drivers or driver versions at this time. To learn more, see Serverless Instance Limitations.
Your database deployment's Connect button may be disabled if your database deployment is in the provisioning state. Your database deployment needs to provision when it is first deployed. Clusters also must provision when you scaled them up or down. The provisoning process can take up to 10 minutes, after which the Connect button will become enabled.
Before connecting to your Atlas database deployment, check that you added your host's IP address to the IP access list for your database deployment's project. Atlas allows client connections only from IP addresses and CIDR address ranges in the IP access list.
To connect to Atlas, you must authenticate with a MongoDB database user. To create a database user for your database deployment, see Configure Database Users.
If you have created a user and are having trouble authenticating, try the following:
Check that you are using the correct username and password for your database user, and that you are connecting to the correct database deployment.
Check that you are specifying the correct
authSourcedatabase in your connection string.
If you have a special character in your password, see Special characters in connection string password.
Atlas sets limits for concurrent incoming connections to a
database deployment. For clusters, this is based on the cluster tier. If
you try to connect when you are at this limit, MongoDB displays an error stating
connection refused because too many open connections.
For a detailed comparision of cluster tiers and their maximum concurrent connections, see Connection Limits and Cluster Tier.
Close any open connections to your database deployment not currently in use.
Scale your cluster to a higher tier to support more concurrent connections.
Restart your application.
To prevent this issue in the future, consider using the
maxPoolSizeconnection string option to limit the number of connections in the connection pool.
To learn how to fix this issue, see Fix Connection Issues.
Atlas can generate an optimized SRV connection string for sharded
clusters using the load balancers from your private endpoint
service. When you use an optimized connection string, Atlas limits
the number of connections per
mongos between your application and
your sharded cluster. The limited connections per
improve performance during spikes in connection counts.
Atlas doesn't support optimized connection strings for clusters that run on Google Cloud or Azure.
To learn more about optimized connection strings for sharded clusters behind a private endpoint, see Improve Connection Performance for Sharded Clusters Behind a Private Endpoint.
Atlas uses a CDN to serve content quickly. If your organization
uses a firewall, add the following Atlas CDN host to the
firewall's allow list to prevent issues accessing the
Atlas database deployments operate on port
27017. You must be able to reach
this port to connect to your database deployments. Additionally, ensure that the
appropriate ports are open for the following:
For sharded clusters, grant access to port 27016.
For BI Connector, grant access to port 27015.
You can check your ability to reach a port using the third-party Outgoing port tester.
To check your ability to reach port 27017, visit http://portquiz.net:27017.
If you can't access these ports, check your system firewall settings and ensure that they are not blocking access to these ports.
If you are using a
mongodb+srv:// connection string and your driver or shell can't find the
DNS host of the Atlas database deployment, the database deployment
might be paused or deleted. Check that the database deployment exists. If
this is a paused cluster, you can resume the cluster if necessary.
Atlas automatically pauses idle
M0 clusters after 60 days
with no connections.
If you use MongoDB Compass to connect to your cluster and experience issues, see:
Connection Refused using SRV Connection String in this section.
Compass Connection Errors in the MongoDB Compass documentation.
In MongoDB Compass, choose Fill in connection fields individually.
In the Authentication dropdown, select
Select More Options.
In the SSL dropdown, select Server and Client Validation.
Add the same path to the downloaded Atlas-managed certificate, or the self-managed certificate (depending on which you use) to each of these fields: Certificate Authority, Client Certificate, and Client Private Key.
To learn more, see Connect to MongoDB in the MongoDB Compass documentation.
The connection string format you use to connect to Atlas depends on several factors, including:
Your driver version. To learn more, see Connect via Your Application.
Verify your connection string in a test environment before putting it into production.
If your password includes special characters, and you are using your password in a connection string URI, encode the special characters.
The following characters must be converted using percent encoding if included in a username or password:
: / ? # [ ] @
For example, if your password in plain-text is
need to encode your password as:
➤ Use the Select your language drop-down menu to set the language of the encoding example in this section.
Do not encode special characters in your password if you are using
your password outside of a connection string URI (for example,
pasting it into
If you see this error message, your driver is likely out of date. For instructions on updating your driver, refer to your specific Driver Documentation.
When you use the DNS seed list connection string format to connect to Atlas, you might see the following error:
DNSHostNotFound: Failed to look up service "<MongoDB service name>"
This error may occur when using the default DNS server that your ISP provides. That DNS server might not support SRV lookups that the DNS seed list connection string format uses.
To resolve the issue, you can try changing your DNS configuration to use a public DNS server.
You can configure your network settings to use Google Public DNS instead of your ISP's DNS servers.
After you update your network settings to use a public DNS server, connect to the database deployment.
If running Ubuntu 18.04 and using the
DNS seed list connection string
mongodb+srv://) to connect to Atlas from one of
the MongoDB Database Tools
mongorestore, etc), you might see the following
lookup nta8e.mongodb.net on 18.104.22.168:27017: cannot unmarshal DNS message
If so, use one of the following connection options instead:
--urioption with a non-SRV connection string (
--hostoption to specify the host to connect.
When using the
DNS seed list connection string
mongodb+srv://) with a driver or Compass, you may
receive in the following error:
Error: querySrv ECONNREFUSED _mongodb._tcp.<SRV Record>
To remedy this issue, use the Standard Connection String format with Compass or that driver. With Compass, don't set the SRV Record value, set the Hostname and Port values instead.