node debugging ai_generated true

Error: Starting inspector on 127.0.0.1:9229 failed: address already in use

ID: node/node-inspector-already-active

Also available as: JSON · Markdown
92%Fix Rate
94%Confidence
50Evidence
2023-01-01First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
20 active — — —

Root Cause

The Node.js inspector (debugger) port 9229 is already in use by another Node.js process or a previous debug session that was not properly terminated.

generic

Workarounds

  1. 95% success Use a different inspector port: --inspect=9230 
    node --inspect=127.0.0.1:9230 app.js — each debug session should use a unique port

    Sources: https://nodejs.org/en/docs/guides/debugging-getting-started

  2. 90% success Find and kill the process using port 9229 
    lsof -i :9229 to find the PID, then kill <PID>

    Sources: https://nodejs.org/api/debugger.html

Dead Ends

Common approaches that don't work:

  1. Running multiple --inspect processes without specifying different ports 90% fail

    All default to port 9229; only the first one succeeds, the rest fail with this error

  2. Killing all Node.js processes to free the port 60% fail

    Kills production processes along with debug ones; overly destructive approach

Error Chain

Leads to:
Preceded by:
Frequently confused with: