# OSError: [Errno 98] Address already in use

- **ID:** `python/flask-debug-reloader-port-in-use`
- **Domain:** python
- **Category:** system_error
- **Verification:** ai_generated
- **Fix Rate:** 80%

## Root Cause

A previous Flask dev server (or the reloader child) is still bound to the port, preventing the new process from binding.

## Version Compatibility

| Version | Status | Introduced | Deprecated |
|---------|--------|------------|------------|
| 3.x | active | — | — |

## Workarounds

1. **** (95% success)
   ```
   lsof -ti:5000 | xargs kill -9
   ```
2. **** (90% success)
   ```
   app.run(port=5001)
   ```

## Dead Ends

- **** — Only avoids the second process; the original is still bound. (80% fail)
- **** — Does not free the port held by the old process. (85% fail)