Database Connection Strings, Demystified

A connection string looks trivial until it isn't. A special character in a password, a missing sslmode, or the wrong scheme for a managed cluster, and you're staring at an authentication error with no obvious cause. Here's how they're actually structured.

The universal shape

Most database URIs follow the same pattern:

scheme://username:password@host:port/database?option=value

Only the pieces change per database:

Database	Scheme	Default port
PostgreSQL	postgresql	5432
MySQL	mysql	3306
MongoDB	mongodb	27017
Redis	redis	6379
SQLite	sqlite	— (file path)

SQLite is the odd one out — it's a file, not a network service:

sqlite:///data/app.db

The gotcha: passwords with special characters

This is the single most common reason a connection string silently breaks. If your password is p@ss:w0rd, this is wrong:

postgresql://admin:p@ss:w0rd@localhost:5432/mydb

The @ and : are structural characters in a URI — the parser sees a different host and port. You must percent-encode them:

postgresql://admin:p%40ss%3Aw0rd@localhost:5432/mydb

@ → %40, : → %3A, / → %2F, and so on. The Database Connection String Builder does this automatically as you type, so you never hit this class of bug. (If you just need to encode one value, the URL Encoder / Decoder handles it too.)

SSL and its many spellings

Every database spells "use TLS" differently:

• PostgreSQL: ?sslmode=require
• MySQL: ?ssl-mode=REQUIRED
• Redis: change the scheme to rediss://
• MongoDB: ?tls=true

Forgetting this against a managed database that requires TLS gives a connection-refused error that looks like a network problem but isn't.

MongoDB's mongodb+srv

Managed MongoDB (like Atlas) uses a DNS seed list instead of a fixed host and port:

mongodb+srv://admin:secret@cluster.example.com/mydb

Note there's no port — the +srv scheme resolves the replica set members via DNS SRV records. Mixing up mongodb:// and mongodb+srv:// is a frequent copy-paste mistake.

JDBC and libpq variants

If you're in the JVM world, the same connection wants a JDBC URL:

jdbc:postgresql://localhost:5432/mydb?sslmode=require

And psql/libpq-based tools accept a keyword/value string:

host=localhost port=5432 dbname=mydb user=admin password=secret sslmode=require

The Database Connection String Builder emits all of these from one form — the URI, the JDBC URL and the libpq string — so you can grab whichever your driver expects. It runs entirely in your browser, so your credentials never leave your machine.