Disable fiddler as system proxy

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Windows
Dwight
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Dwight asked on 30 Mar 2017, 05:18 AM

I have one specific browser instance that I have configured to always use fiddler, I turn on and off others as needed.   I'm doing development work and I want to see what's actually being sent back and forth, but, I really only care about my stuff.

I launch fiddler with my PC, and I have the "Capture traffic" turned off and the setting "Act as system proxy on startup" is not checked in the connections tab.

Other application on my system are still finding and using fiddler as it's proxy server, frequently causing failures.

How do I "hide" fiddler so that other systems like skype and google drive don't use it?   

It impacts me negatively in 3 ways. 

First, I only want to see traffic that I send to fiddler, I have to go out and delete a bunch of stuff.  I can remove them with filters and probably find a way to make my filters "stick" and survive reboot.   I'd have to research that.

Second and more importantly, I decrypt https, which fails on application that are not configured to use the self generated signatures.

Third, when I do shut down fiddler, the apps that have auto-detected it and configured themselves to use fiddler, still want to use fiddler.

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Tsviatko Yovtchev
Telerik team
answered on 04 Apr 2017, 04:35 PM
Hi,

When Fiddler is capturing traffic it sets itself as the WINInet proxy system wide. Any app that uses WINInet proxy settings will redirect its traffic through Fiddler in that case. When it shuts down it should restore the original proxy settings so the apps should switch back to not using FIddler as a proxy. Now an app might not keep an eye on WINInet proxy changes and that might explain part of what you see. The Act as System Proxy on startup setting though should work. Are you sure Fiddler still starts capturing traffic with that off? What is in your proxy settings at that moment?

Regards,
Tsviatko Yovtchev
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TJ
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commented on 14 Aug 2017, 03:35 PM

Tsviatko,

I am new Fiddler user.

Basically, I do not think Fiddler automatically restores the original proxy settings.  I had to completely uninstall Fiddler due to ALL browsers on my computer (IE, Chrome, and Firefox) received an error of "proxy server isn’t responding" or something along those lines.  For me to reach the Internet, I removed Fiddler and rebooted my PC.  

 

Is there a setting or registry entry I should check/change to ensure Fiddler restores the original proxy settings when I shutdown Fiddler?

 

T.J.

Alexander
Telerik team
commented on 17 Aug 2017, 02:52 PM

Hi,

No, there is no such setting. If Fiddler has "Act as system proxy at startup" enabled, it should restore the original proxy settings on shutdown automatically.

You can check the current proxy settings by going to "Internet Options -> Connections -> LAN settings". If the "Use a proxy server for your LAN" setting is checked, in "Advanced" the proxy address is set to 127.0.0.1 and the port is set to the port Fiddler is listening at (the default is 8888), then Fiddler is set as proxy. You can easily stop it from being proxy by unchecking the "Use a proxy server for your LAN" setting or by changing the address/port combination (if you are using proxy server). There is no need to restart your PC or to remove Fiddler.

Regards,
Alexander
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Steven
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commented on 03 Jan 2018, 03:46 PM

Hi. When the proxy setting is altered my site no longer responds and all internet connection is no longer valid on all browsers and i get an error pop up on the page. See attached, is there a way around this issue.  

Regards 
S

Suresh
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commented on 13 Mar 2018, 10:06 PM

Hi, This is Suresh. When Fiddler setting up it's own proxy application not loading on IE and if I uncheck the proxy settings Fiddler not capturing the traffic. Please suggest if any workaround.
Pieter
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commented on 19 Jul 2018, 08:19 AM

Telerik resets the automatic set script for me. We don't use the manual proxy server setting so I cannot say whether that gets reset.

I have a slightly different problem where my internet stop working after a while and I have to manually reset the settings and click the yellow bar in Fiddler.

Alexander
Telerik team
commented on 23 Jul 2018, 09:15 AM

Hello Pieter,

Which yellow bar in Fiddler you have to click (since there are several)? I assume you are talking about the "The system proxy was changed. Click to reenable capturing." one. If you are talking about this one, then some other software (VPN, AV) is changing the proxy settings of the machine.

Regards,
Alexander
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Roger
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answered on 06 Dec 2018, 12:25 PM

I had a issue where Fiddler got stuck as system proxy even though it did not appear when viewing "inetcpl.cpl" >> Connections >>  LAN Settings.  This had the result of Windows Metro/UWP apps and VS2017 NuGet Package Manager unable to access the internet without Fiddler running, in Windows 10 17134.441

What seemed to fix it was unchecking and rechecking "Capture Traffic" with Fiddler running.  My computer may have had a lockup as some point with fiddler running and a hard reboot may have left a stray setting somewhere that was messing with internet traffic through the 127.0.0.1:8888 proxy.

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Rob
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answered on 24 Mar 2020, 07:05 AM

 "inetcpl.cpl" >> Connections >>  LAN Settings | untick Use Proxy Server

This setting did not reset to unticked after Fiddler was uninstalled.

Eric R | Senior Technical Support Engineer
Telerik team
commented on 24 Mar 2020, 06:26 PM

Hi Rob,

Sorry to hear that Fiddler didn't remove the Proxy configuration upon uninstallation. This could be caused by different scenarios. 

1. The most common is where Fiddler crashed and was uninstalled before resetting the configuration. However, once the configuration is reset using LAN Settings it should be fixed.

2. Alternatively, there may be additional software interfering. For example, a VPN, or Firewall/Security Software. This could happen if the software is forcing the ProxyServer as readonly and would need to be reset by disabling the offending application and then resetting the proxy.

3. The least common is the Windows Configuration is corrupt. This can happen in bugs with the WinINET Networking Library. In order to resolve this I recommend contacting Microsoft Support to get more information on how to repair Windows.

I hope this helps. Please let me know if you need any additional information. Thank you for using the Fiddler Forums.

Regards,


Eric R | Senior Technical Support Engineer
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Kyle
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commented on 10 Jan 2021, 07:19 AM

Hi have a similar issue to these people. I am completely new at this fiddler thing and I have no idea what it does. I just know that I can't connect to anything without having fiddler on otherwise it just keeps loading and says I cannot connect to the internet. I uninstalled it and everything and it will not go back to the way it was. I want nothing to do with this program anymore I just want my pc back for everyday use without having to launch fiddler every time to connect to discord or steam etc. Thanks.
Rosen Vladimirov
Telerik team
commented on 11 Jan 2021, 03:26 PM

Hi Kyle,

I've already answered this question in your other post here. Please take a look at it and lets keep the conversation on a single place.

Regards,
Rosen Vladimirov
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Dwight
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Tsviatko Yovtchev
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Roger
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Rob
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