MongoDB Connection String Builder

Q: What is the default MongoDB port?

27017. If your server listens on a different port, include it explicitly as host:port. DNS seedlist (mongodb+srv) URIs don't use an explicit port.

Q: What is the difference between mongodb:// and mongodb+srv://?

mongodb:// lists servers explicitly; mongodb+srv:// takes a single hostname and resolves the member list and default options from DNS. MongoDB Atlas provides the +srv form, and it enables TLS by default.

Q: My MongoDB password has special characters, will it work?

Yes. Characters like @, :, /, ? and # must be percent-encoded in the URI. This builder encodes the username and password for you.

More information about MongoDB connection strings

Almost every MongoDB driver and tool, from mongosh to Compass to your application code, connects using a connection string URI. This guide explains how a MongoDB URI is structured, what each part does, and which options you'll reach for most often.

What is a MongoDB connection string?

A connection string is a single URL that tells a MongoDB driver where your database lives and how to connect to it, the servers, the credentials, and any connection options. Instead of configuring host, port and auth separately, you pass one string and the driver parses the rest.

The two URI schemes

mongodb://, the standard scheme. You list one or more host:port pairs explicitly. Used for standalone servers, replica sets, and sharded clusters.
mongodb+srv://, the DNS seedlist scheme. You give a single hostname and MongoDB looks up the actual servers (and default options) from DNS SRV/TXT records. This is what MongoDB Atlas hands you, and TLS is enabled by default.

Components of a MongoDB URI

General format

mongodb://[username:password@]host1[:port1][,host2[:port2]...]/[database][?options]

mongodb://, the scheme (or mongodb+srv:// for DNS seedlist).
username:password@, optional credentials. Special characters must be percent-encoded (this tool does that for you).
host:port, one or more servers, comma-separated. The default port is 27017.
/database, the optional default (and default auth) database.
?options, connection options as key=value pairs joined with &.

Example

mongodb://appUser:s3cret@db1.example.com:27017,db2.example.com:27017/shop?replicaSet=rs0&authSource=admin&tls=true

This connects to a two-member replica set rs0, authenticates user appUser against the admin database, selects the shop database, and requires TLS.

Common options

Authentication

authSource, the database to authenticate against (often admin).
authMechanism, SCRAM-SHA-256 (default), MONGODB-X509, PLAIN (LDAP), MONGODB-AWS, or GSSAPI.

Topology

replicaSet, the replica-set name; required to connect as a set rather than to a single node.
readPreference, primary (default), primaryPreferred, secondary, secondaryPreferred, or nearest.

Security & reliability

tls (a.k.a. ssl), enable encrypted connections.
retryWrites / retryReads, automatically retry once on transient network errors (both default to true).
w, write concern, e.g. majority.

Performance

maxPoolSize / minPoolSize, connection-pool bounds (default 100 / 0).
connectTimeoutMS / socketTimeoutMS / serverSelectionTimeoutMS, timeouts.
compressors, wire compression (snappy, zlib, zstd).
appName, an identifier that shows up in server logs and profiling.

Tips for building a MongoDB URI

Percent-encode credentials. Usernames and passwords with @, :, / or other special characters must be encoded, this builder handles it automatically.
Keep it clean. Only set options that differ from the defaults; extra parameters make the string harder to read. This tool omits defaults for you.
Prefer SRV for Atlas. mongodb+srv:// keeps the string short and lets the cluster manage its own member list.
Don't hardcode secrets. Load the connection string from an environment variable or a secrets manager instead of committing it.

Frequently asked questions

What is the default MongoDB port?

27017. If your server listens on a different port, include it explicitly as host:port. (DNS seedlist URIs don't use an explicit port.)

What's the difference between mongodb:// and mongodb+srv://?

mongodb:// lists servers explicitly; mongodb+srv:// takes a single hostname and resolves the member list and default options from DNS. Atlas provides the +srv form, and it enables TLS by default.

My password has special characters, will it work?

Yes. Characters like @, :, /, ? and # must be percent-encoded in the URI. This builder encodes the username and password for you.

Do I need authSource?

Only when your user is defined in a database other than the one you're connecting to (commonly admin). The builder adds authSource only when it differs from MongoDB's default.