MongoDB Connection String Format

MongoDB URI Format

MongoDB uses the mongodb:// URI scheme (or mongodb+srv:// for SRV-based connections). The format is:

mongodb://[user[:password]@]host[:port][/database][?options]

Authentication Parameters

MongoDB authentication requires three key pieces:

1. Username and password in the URI authority section
2. authSource — the database used to verify credentials (defaults to admin)
3. authMechanism — the authentication method (default is SCRAM-SHA-256)

Example with explicit auth source:

mongodb://appuser:p4ssw0rd@localhost:27017/myapp?authSource=admin

Replica Set Connections

For replica set clusters, list all members separated by commas:

mongodb://host1:27017,host2:27017,host3:27017/mydb?replicaSet=rs0

The driver will discover the full topology from any reachable member, but listing multiple nodes ensures connectivity even if one is down.

Common Options

Parameter	Purpose	Example
authSource	Auth database	admin
replicaSet	Replica set name	rs0
retryWrites	Auto-retry writes	true
w	Write concern	majority
readPreference	Read routing	secondaryPreferred
maxPoolSize	Max connections	50
tls	Enable TLS	true

Full Production Example

mongodb://appuser:str0ngP%40ss@mongo1.example.com:27017,mongo2.example.com:27017/production?authSource=admin&replicaSet=rs0&retryWrites=true&w=majority&tls=true

This string connects to a two-member replica set with authentication against the admin database, automatic write retries, majority write concern, and TLS encryption.