MaxListenersExceededWarning 🟩 Node.js

MaxListenersExceededWarning: Possible EventEmitter memory leak detected. 11 listeners added

More than 10 listeners were added to one event — often a leak where listeners are added repeatedly.

Seen on: Node.js

Meaning

Adding a listener on every request/loop iteration without removing it grows memory. Sometimes legitimate many listeners need a higher limit.

Common causes

  • Adding listeners inside a request handler or loop
  • Not removing listeners on cleanup
  • Many legitimate subscribers

⚡ Quick fix

  1. Add listeners once, outside loops
  2. Remove with off()/removeListener on cleanup
  3. Raise the limit only if legitimate: emitter.setMaxListeners(20)

Detailed fix by platform

Node.js

  1. node --trace-warnings app.js shows where listeners are added

How to diagnose

  1. Event — Which event/emitter?
  2. Growth — Does it keep increasing?

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