How to auto reset Fiddler when 'system proxy was changed'

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Alex
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Alex asked on 02 Mar 2014, 08:01 PM
From time to time, sometimes a few times a day, Fiddler would show a yellow bar and a message "The system proxy was changed. Click to reenable Fiddler capture".
Is there a way to make the re-enabling happen automatically? 
I just want Fiddler always running so I don't have to re-enable it.

Thanks.

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Eric Lawrence
Telerik team
answered on 05 Mar 2014, 07:02 PM

Hi, Alex--

To reestablish Fiddler as the system's default proxy, you must click the yellow bar. To avoid having to click the bar, your best bet is to determine what other application is changing your system's proxy settings and disable it from doing so (VPN software and firewall clients like ISA/TMG are common culprits).



Fiddler does not automatically attempt to reestablish itself as the proxy as this could lead to an infinite loop, whereby it and the other software "fight" over the proxy setting in an endless loop.



-Eric

a.ateeque
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commented on 09 Apr 2014, 10:08 AM

Hi Eric
I am facing the same problem.
Is there any way to figure out what other applications may be changing the proxy settings? Can the client's proxy config be changed by a remote application?
Thanks!
Eric Lawrence
Telerik team
commented on 09 Apr 2014, 06:45 PM

Generally speaking, no, remote applications cannot change your local system's proxy settings, unless the remote application has a client on your computer. For instance, if your company uses Group Policy or login scripts, those can write to the system's registry using code on your local computer.

If you don't have any programs known to change the system proxy installed (e.g. ProxySwitchers, ISA Firewall Client, TMG Firewall client, etc) then your best bet would be to download Process Monitor from SysInternals and set a filter for registry WRITEs where the path contains PROXYSERVER. This will show you all writes to the proxy server registry key, which will help you determine which process is changing the proxy behind your back.

Regards,
Eric Lawrence
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André
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commented on 02 Dec 2014, 12:15 PM

I have this problem too such a degree that fiddler is useless... The error comes up every other second and when I reenable Fiddler capture it takes maximum 1 sec before the message is there again. 

I have tried to turn off everything I can think off as well as trying to monitor all changes to PROXYSERVER with Process Monitor. 

What more can I do!?
Eric Lawrence
Telerik team
commented on 02 Dec 2014, 11:43 PM

Unfortunately, unless you find the software changing your settings, you can't resolve this.

Let's step back a bit though... when the notification appears, don't click it. Instead, click Tools > WinINET Options. Click the "LAN SETTINGS" button on the CONNECTIONS tab.

What are the contents of this screen, and, if it's enabled, the contents of the screen shown when the Advanced button is clicked?

Regards,
Eric Lawrence
Telerik
 

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André
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commented on 03 Dec 2014, 11:47 AM

My process monitor wasn't configured properly. When I experimented with it for a while I managed to find out that it was a Wajam application that was writing constantly to the proxy. So removing it solved the issue. 

Thanks for this thread!
Screw
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commented on 19 Feb 2015, 06:37 PM

My VPN client (Big IP Edge Client, F5 Networks) keeps doing this. I cannot use Fiddler while I'm on the VPN due to this. Just thought I'll post a note for others who might be using this VPN client.
Peter
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commented on 19 Sep 2015, 07:00 AM

Just to add to this list: Hola.org also seems to be causing this.
Eric Lawrence
Telerik team
commented on 21 Sep 2015, 06:19 PM

While disabling software that makes unwanted changes to your proxy setting is the best approach, some users may find the approach outlined here: http://www.telerik.com/forums/how-to-automatically-re-enable-fiddle-as-system-proxy sufficient.

Regards,
Eric Lawrence
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Tony
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commented on 30 Sep 2015, 08:30 PM

The link is broken and Google doesn't bring up the post when searching for those keywords
Eric Lawrence
Telerik team
commented on 30 Sep 2015, 08:49 PM

Hello, Tony--

The link is http://www.telerik.com/forums/how-to-automatically-re-enable-fiddle-as-system-proxy

Regards,
Eric Lawrence
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William
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commented on 11 Jul 2019, 09:12 AM

when I click the YELLOW BAR(the system proxy was changed. click to reenable capturing), I find Fiddler does the changes in windows registry and capture it as pic 1.

After waiting for a while, fiddler makes some changes to the windows registry again, then the yellow bar shows up. (refer to pic 2)

 

seems it is Fiddler who causes this issue.

 

 

Kammen
Telerik team
commented on 16 Jul 2019, 07:44 AM

Hello William,

Thank you for contacting us. 

We're unable to reproduce this. Can you specify what is causing Fiddler to show the yellow bar?

Regards,
Kammen
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manigandan
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commented on 20 Jul 2020, 11:30 PM

Hi, I am getting the error as attached. This was introduced recently. When i click on enable it stays and then it shows the same error. please help out. Attached the screen. even though i disable the setting in IE, it keeps on enabling automatically. Please help to resolve this issue in fidder to work independently without IE settings.

 

Eric R | Senior Technical Support Engineer
Telerik team
commented on 21 Jul 2020, 03:35 PM

Hi Manigandan,

Thank you for providing the screenshot. It appears that the machine in use is being managed by a Corporate Policy. In this case, we are unable to provide a workaround. I recommend reaching out to your IT department and asking them if it is possible to relax or bypass the policy. 

Please let me know if you need any additional information. Thank you.

Regards,


Eric R | Senior Technical Support Engineer
Progress Telerik

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Tony
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answered on 30 Sep 2015, 10:32 PM

 

I too get the yellow bar several times a day. When I check the lan settings, I don't see a difference. All the checkboxes are always unchecked. Unless there's an app which changes it momentarily, I am not sure why Fiddler thinks the proxy settings have changed.

 

Eric says if he enables auto re-enabling, a race condition or an infinite loop will happen. I am not sure if this would happen every time and if it does happen, then Fiddler can detect this scenario and display a message saying that it tried several times to reenable it within x period of time and it gave up and will stop trying to re-enable it.

Anyways, I will try the re-enabling code mentioned in another post.

 

Eric Lawrence
Telerik team
commented on 01 Oct 2015, 04:39 PM

Hi, Tony--

> "All the checkboxes are always unchecked." 

And that's a problem. While Fiddler is capturing, it sets the proxy settings to point to itself. If the proxy settings are cleared by other software, traffic will no longer flow to Fiddler.

You can use Process Monitor to watch for writes to the ProxyServer registry key to see what software is whacking your proxy settings; typically this is caused by networking or VPN software.

Regards,
Eric Lawrence
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Tony
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commented on 01 Oct 2015, 08:35 PM

I ran Process Monitor and had two filters. One on path contains 'proxyserver' and one on operation contains 'set'. The attached capture shows all the changes are done to registry keys which belong to TrendMicro. I don't see keys belonging to the system's proxyserver. Yet these changes have triggered Fiddler's warning.

Eric Lawrence
Telerik team
commented on 02 Oct 2015, 07:37 PM

Hi--

It may well be the case that TrendMicro is the culprit here (insofar as they're known to attempt to run traffic through tmproxy.exe in order to "scan" it). 

If you don't see writes to the ProxyServer key, try watching for writes to the ProxyEnable key instead.

Regards,
Eric Lawrence
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John
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commented on 19 Feb 2016, 04:28 PM

I downloaded Process Monitor, but I am getting overwhelmed with events. Over 1 million. How do I filter? Also, what am I looking for? My proxy gets changed instantly. When I click on the yellow bar, it instantly gets changed back. I know it's an IBM product doing it. I believe they calle it "zScaler" around here.
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Mohamed Amine
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answered on 21 Jun 2018, 08:32 PM
restart it
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