MongoDB Atlas SRV Connection String (mongodb+srv://)

MongoDB Atlas and SRV Connections

MongoDB Atlas uses the mongodb+srv:// protocol, which leverages DNS SRV records to automatically discover cluster members without listing individual hostnames.

Standard vs SRV Format

Standard format (listing each host):

mongodb://user:pass@shard1.example.com:27017,shard2.example.com:27017,shard3.example.com:27017/mydb?replicaSet=atlas-xxx&ssl=true

SRV format (Atlas recommended):

mongodb+srv://user:pass@cluster0.abc123.mongodb.net/mydb?retryWrites=true&w=majority

The SRV format is shorter, more readable, and automatically discovers all cluster nodes via DNS.

How SRV Works

When a MongoDB driver sees mongodb+srv://, it performs two DNS lookups:

1. SRV record for _mongodb._tcp.cluster0.abc123.mongodb.net — returns the actual hostnames and ports of all cluster members
2. TXT record for cluster0.abc123.mongodb.net — returns default connection options (e.g., authSource=admin&replicaSet=atlas-xxx)

This means the cluster can add/remove nodes or change ports without requiring connection string updates in your application.

Atlas Connection String from the Dashboard

MongoDB Atlas generates your connection string automatically:

1. Go to your Atlas cluster
2. Click Connect
3. Choose your driver (Node.js, Python, etc.)
4. Copy the connection string and replace <password> with your actual password

Common Atlas Options

mongodb+srv://user:pass@cluster0.abc123.mongodb.net/mydb?retryWrites=true&w=majority&appName=myapp

Parameter	Purpose
retryWrites=true	Automatically retry failed writes
w=majority	Writes acknowledged by majority of nodes
appName=myapp	Identifies your app in Atlas monitoring
maxPoolSize=50	Maximum connection pool size
readPreference=secondaryPreferred	Read from secondaries when possible

Important Notes

• No port number — SRV connections resolve ports via DNS, so you omit the port
• TLS is always enabled — Atlas requires TLS; the SRV protocol enables it by default
• Password encoding — Special characters in passwords must be percent-encoded (use this tool to handle that automatically)
• IP Access List — Atlas requires your IP to be whitelisted. Use 0.0.0.0/0 for development only; restrict to specific IPs in production