MongoDB: MongoParseError: Invalid scheme, expected connection string to start with "mongodb://" or "mongodb+srv://"
The connection string is missing, malformed, or the environment variable holding it is undefined.
Exact message you may see
Invalid scheme, expected connection string to start withURI malformedPassword contains unescaped charactersThe `uri` parameter to `openUri()` must be a string, got "undefined"
Seen on:
MongoDB
Meaning
The driver received undefined/empty, a string with quotes or spaces, or a URI with unescaped special characters (MongoParseError: URI malformed / Password contains unescaped characters).
Common causes
- MONGODB_URI env var not loaded (undefined)
- Quotes or whitespace around the value
- Unescaped @ : / in username/password
- Copied a placeholder like <password>
⚡ Quick fix
- Log whether the env var is set (not its value)
- Remove quotes/spaces
- URL-encode credentials
Detailed fix by platform
JavaScript
- javascript
import "dotenv/config"; if (!process.env.MONGODB_URI?.startsWith("mongodb")) throw new Error("MONGODB_URI missing or invalid"); await mongoose.connect(process.env.MONGODB_URI);
How to diagnose
- Env — Variable loaded?
- Format — Scheme and characters
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Last updated 13 Oct 2026