MongoServerSelectionError 🟩 Node.js

MongooseServerSelectionError: connect ECONNREFUSED 127.0.0.1:27017

The MongoDB driver couldn’t find a reachable server for the connection string.

Seen on: Node.js

Meaning

Local mongod not running, Atlas IP access list blocking you, DNS SRV failures (mongodb+srv), TLS problems, or localhost resolving to IPv6.

Common causes

  • mongod not running locally
  • Atlas Network Access not including your IP
  • mongodb+srv DNS lookup failing
  • localhost → ::1 while mongod listens on IPv4

⚡ Quick fix

  1. Start MongoDB / check the Atlas cluster
  2. Add your IP in Atlas
  3. Use 127.0.0.1 instead of localhost
  4. Test with mongosh using the same URI

Detailed fix by platform

Node.js

  1. mongoose.connect('mongodb://127.0.0.1:27017/app')

How to diagnose

  1. Reason — The nested reason (ECONNREFUSED, ETIMEOUT, ENOTFOUND)
  2. Access — IP allowed?

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