Not capturing web traffic automatically

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MacOS
John
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John asked on 22 May 2017, 11:15 PM

Hello, I have downloaded Fiddler for Mac from this link: https://www.telerik.com/download/fiddler and have followed the installation instructions regarding mono and placing fiddler.exe in a writable directory. When running "mono fiddler.exe" from my terminal, Fiddler starts up. However, it is not automatically capturing web traffic like I am used to it doing on Windows.

Is there some other step that I need to perform on Mac for it to start capturing web traffic?

- John

Tsviatko Yovtchev
Telerik team
commented on 29 May 2017, 06:19 PM

F12 toggles capture on and off. It should be on by default though. Is it not? Does it start capturing if you turn it on?

Regards,
Tsviatko Yovtchev
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Neha
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commented on 15 Jun 2017, 11:37 AM

For me, I had to download root certificate the device which I am trying to connect to . You can install that certificate from http://ipv4.fiddler:8888/ and download FiddlerRoot certificate. Hopefully, then the device traffic will be shown to you.

Neha

Xiaosong
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commented on 16 Aug 2017, 11:03 PM

I downloaded Fiddler today, together with mono 5.0 (5.2 doesn't start Fiddler), however, it doesn't capture anything (F12 is on).

I tried to export root cert from Tools->Option-->Https tab, and imported cert to both Chrome and  Firefox, made it "trusted", but still not capture. My mac version is Sierra (10.12.6).

Any idea?

Thanks

Alexander
Telerik team
commented on 21 Aug 2017, 05:04 PM

Hello,

It sounds like Fiddler is not a proxy for Chrome and Firefox. At startup Fiddler tries to set itself as a machine-wide proxy, but this requires sudo permissions. Did you enter your credentials when asked?

Regards,
Alexander
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Xiaosong
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commented on 21 Aug 2017, 09:55 PM

Hi,

Yes, I credentials when asked (several times).

 

Thanks

Olivier
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commented on 25 Aug 2017, 03:36 PM

Same problem here.

No capture at all.
I'm interested in https traffic though.

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Alexander
Telerik team
answered on 28 Aug 2017, 12:51 PM
Hi,

We've tested Fiddler on Sierra 10.12.6 and everything worked, so it may be machine-specific or setup-specific problem. Would it be possible that you let me know what is the Terminal output?

As a workaround you can set Fiddler as proxy manually. To do that go to System Preferences -> Network -> Advanced -> Proxies and set the HTTP and HTTPS proxies to point to Fiddler. As a host enter 127.0.0.1 and for port you can check Fiddler's Help -> About. It is 8888 by default.

Regards,
Alexander
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Olivier
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commented on 29 Aug 2017, 08:22 AM

Setting the proxy manually solved the problem. Fiddler now is capturing traffic.
Neha
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commented on 30 Aug 2017, 05:36 AM

Can you send me the link from where I can download fiddler which is compatible with Sierra 10.12.5? 
Glenn
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commented on 29 Jul 2018, 11:12 PM

Hi Admins,

I've got almost exactly the same issue here.

 

I have:

✅ Downloaded and installed the latest Mono 5.0.x (5.0.1.1) so that I'm always on the 32-bit mode.

✅ Downloaded and installed the latest fiddler-mac (https://www.telerik.com/download/fiddler).

✅ Made sure "Capture Traffic" (F12) is on.

✅ "Decrypt HTTPS Traffic" (...from browsers only) is checked.

✅ Exported root certificate to Desktop, then imported it to the Keychain Access and made it trusted.

✅ Checked the HTTP and HTTPS proxies correctly pointed to 127.0.0.1:8888.

 

I am:

  • on MacOS El Capitan (10.11.6).
  • not behind the VPN.
  • using Chrome and Safari.

 

I'm still not seeing anything in my Fiddler except this one particular request to https://fiddler2.com (please see the attached screenshot). Any more ideas what could've I missed? I'm a bit suspicious that Fiddler doesn't act as my proxy somehow.

 

Alexander
Telerik team
commented on 02 Aug 2018, 04:17 AM

Hello Glenn,

Click on the "Web Browsers" in the status bar and change it to "All processes". Also change to "All processes" the settings for the HTTPS decryption in Tools -> Options -> HTTPS. Does this make any difference?

Regards,
Alexander
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Glenn
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commented on 02 Aug 2018, 08:20 AM

That's it!! Changing the filter from "Web Browsers" to "All processes" works for me. Thank you so much for saving me from being mad, Alex.

But still, not sure why the requests from the browsers are considered to be "Non-Browser" requests. 🤔 Bug?

Alexander
Telerik team
commented on 02 Aug 2018, 10:46 AM

Hi,

The current version of Fiddler for Mac does not work that well and have some quirks like that one. The good news is that newer version is comming. You can find more information here.

Regards,
Alexander
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Glenn
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commented on 03 Aug 2018, 08:43 AM

Thank you,

I'll keep an eye on it. 👀
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Xiaosong
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answered on 28 Aug 2017, 07:38 PM

Hi Alexander,

Just found the problem is caused by VPN. After disabled VPN, Fiddler works. What setting does it need when connected with VPN?

Terminal output is just "wi-fi", nothing else. Proxies is set as you suggested.

Thanks

Alexander
Telerik team
commented on 05 Sep 2017, 10:33 AM

Hello Xiaosong Li,

In order to Fiddler to capture traffic it has to be proxy, in this case - proxy of the VPN. However, this is not a Fiddler-related problem, but rather a network configuration problem, so I'm unable to guide you any further.

Regards,
Alexander
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