Windows pop-up message as belows:

Unable to bind to port [Localhost:8888]. ErrorCode: 10048.

This is usually due to another service running on this port. Run NETSTAT -A at a command prompt.

What can I do?


  • Try asking on superuser.com ?
    – Paul R
    Jun 21, 2010 at 15:03
  • 1
    Did you run netstat -a, as instructed? What was the result? Jun 21, 2010 at 15:21

2 Answers 2


Tools menu -> Fiddler Options -> Connections tab -> Fiddler listens on port

There you can change the port that Fiddler uses.

  • I couldn't edit this field, so I ran fiddler from the command line and specified the port: Fiddler.exe -port:0 (zero for random in this example)
    – Hoppe
    Nov 10, 2017 at 20:45

I had a similar situation while working with my local web server. After this error message Fiddler didn't monitor any of my connections from the browser.

I did changed port on 8085 in Fiddler Options -> Connections tab -> Fiddler listens on port: but I also checked check box "Act as system proxy on startup", and after restart it started to work as usual.

I hope it helps.

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