Pending Review
Last Updated: 17 Oct 2019 03:55 by Ray

I'm using Fiddler [Oct-03-19] v5.0.20194.41348 on Windows 7 Enterprise. There's no way to disable the 'Get Started' panel on startup. 'Show on startup' is not checked but it still shows. Also it doesn't look very good. Also it downloads javascript and other stuff via http unencrypted from, and I'd like to stop that.


Pending Review
Last Updated: 15 Oct 2019 11:46 by S

Once a program has been "Filter now"ed via the context menu, if that filter is later deleted from down bottom, that program can no longer be "Filter Now"ed again; nothing happens.

It's as if program filtering is only given one opportunity to be "Filter Now"ed. Once that's happened, even if they filter gets deleted, the program isn't given another opportunity to be Filter Now'ed.

Pending Review
Last Updated: 19 Sep 2019 19:11 by ADMIN
Created by: Antonio
Comments: 3
Type: Bug Report

Fiddler crashes sometimes with this message:

No se puede obtener acceso al objeto desechado.

Nombre del objeto: 'WinHttpAutoProxy'.

Type: System.ObjectDisposedException
Source: Fiddler
   en “.Ÿœ.ƒ•(String •, String& ‘‰, String& ”) en C:\JenkinsHome\jobs\FiddlerReleaseBuild\workspace\FiddlerCore\PlatformExtensions\Windows\FiddlerCore.PlatformExtensions.Windows.Shared\WinHttpAutoProxy.cs:línea 52
   en .‚•.œ(String –, IPEndPoint& žœ) en C:\JenkinsHome\jobs\FiddlerReleaseBuild\workspace\Fiddler2\Common\Core\AutoProxy.cs:línea 142
   en Fiddler.Proxy.FindGatewayForOrigin(String sURIScheme, String sHostAndPort) en C:\JenkinsHome\jobs\FiddlerReleaseBuild\workspace\Fiddler2\Common\Core\Proxy.cs:línea 805
   en Fiddler.ServerChatter.Œ() en C:\JenkinsHome\jobs\FiddlerReleaseBuild\workspace\Fiddler2\Common\Core\ServerChatter.cs:línea 1056
   en Fiddler.ServerChatter.‹Œ(AsyncCallback ŒŒ) en C:\JenkinsHome\jobs\FiddlerReleaseBuild\workspace\Fiddler2\Common\Core\ServerChatter.cs:línea 932
   en Fiddler.Session.‘() en C:\JenkinsHome\jobs\FiddlerReleaseBuild\workspace\Fiddler2\Common\Core\Session.cs:línea 3638
   en Fiddler.Session.œ™(IAsyncResult Œ) en C:\JenkinsHome\jobs\FiddlerReleaseBuild\workspace\Fiddler2\Common\Core\Session.cs:línea 3649
   en Fiddler.ServerChatter.ŽŒ() en C:\JenkinsHome\jobs\FiddlerReleaseBuild\workspace\Fiddler2\Common\Core\ServerChatter.cs:línea 1518
   en Fiddler.ServerChatter.Œ() en C:\JenkinsHome\jobs\FiddlerReleaseBuild\workspace\Fiddler2\Common\Core\ServerChatter.cs:línea 1472
   en Fiddler.ServerChatter.‹Œ(AsyncCallback ŒŒ) en C:\JenkinsHome\jobs\FiddlerReleaseBuild\workspace\Fiddler2\Common\Core\ServerChatter.cs:línea 932
   en Fiddler.Session.‘() en C:\JenkinsHome\jobs\FiddlerReleaseBuild\workspace\Fiddler2\Common\Core\Session.cs:línea 3638
   en Fiddler.Session.(Object ) en C:\JenkinsHome\jobs\FiddlerReleaseBuild\workspace\Fiddler2\Common\Core\Session.cs:línea 3426

Fiddler v5.0.20173.50948 (x86 x86) [.NET 4.0.30319.42000 on Microsoft Windows NT 6.1.7601 Service Pack 1] 

Pending Review
Last Updated: 17 Sep 2019 00:39 by Eric

Hello sir, 

         I've discovered the security bug with is privilege escalation bug via DLL sideloading.

please check it for more details:



Pending Review
Last Updated: 04 Sep 2019 16:04 by Dave
Created by: Dave
Comments: 7
Type: Feature Request

It would be really great to be able to view requests and responses as a formatted json string.  Currently, you can show JSON, which uses some tree format, and you can show raw, which is just a flat hard to use string.

It would also be great to be able to format json inside the request composer so it can be easy to modify.

Pending Review
Last Updated: 23 Aug 2019 13:15 by Gary


I have a connectivity issue when I run Fiddler (Progress Telerik Fiddler Web Debugger). I work behind a corporate proxy server and the server IP is changed every few hours. The change in IP is normally okay, but when I am running Fiddler with the 'Automatically Authenticate' option enabled, then Fiddler shows an error every time the proxy is changed; it shows a yellow error message suggesting "The system proxy was changed. Click to reenable capturing".

Clicking on the error in Fiddler works fine and it reconnects, but I find this frustrating because if i don't realise there was an error in fiddler and don't click it immediately then it affects my connectivity and some activities on my pc start to fail without me realising.

My suggestion is that you should let Fiddler auto-reconnect when this type of proxy change happens and when the 'Automatically Authenticate' option is enabled. I know it can't try to reconnect forever because it will cause an endless cycle for other people who have other types of proxy disconnects, but in my case it would be very helpful to let fiddler at least try once to auto reconnect (for me 1 retry is usually fine and Fiddler is able to connect to the new proxy address, but perhaps you can let the number of retries be a menu option so that users can set the number of retries that they want Fiddler to do after there was a proxy change or proxy error).


Thanks so much for your work, I really like Fiddler!

I hope you can bug fix this or add it as a feature, it will be very helpful!



Pending Review
Last Updated: 20 Aug 2019 22:38 by ADMIN
Created by: Jonny
Comments: 1
Type: Feature Request


Is there any way to disable underlining of URL in Raw Inspector tab? It is very annoying when you try to copy part of the request but in fact open the link in the browser instead.

Pending Review
Last Updated: 14 Aug 2019 03:17 by Eric

It would be great to have an option in the textWizard to convert an epoch date to a human-readable date.

Like: 1530417600 to "GMT: Tuesday 13 August 2019 08:32:48"


It would be great to have 2 options:

- convert epoch time to human readable time (GMT timezone)

- convert epoch time to human readable time (Local timezone)


Thanks for creating one of the most useful tools ever!

Pending Review
Last Updated: 08 Jul 2019 19:05 by James


Fiddler does not set up it's proxy server for the websocket protocol.  Applications looking at the global proxy settings are told by WebRequest.DefaultWebProxy.IsBypassed(Uri) that no proxy server should be used for the specified wss Uri.


Replication steps:

1. Have a .NET application that uses websockets and checks WebRequest.DefaultWebProxy.IsBypassed(Uri) to see if a proxy should be used for a wss Uri.

2. Try to use Fiddler to observe websocket traffic



After turning on fiddler, enable "Use the same proxy server for all protocols" in the Internet Options / Advanced Proxy settings screen.

Pending Review
Last Updated: 03 Jul 2019 10:10 by Tony

Fiddler is a great tool & Composer an excellent feature of it.  I frequently have to reboot my dev. PC  for various reasons (actually it crashes a lot) and loosing my Composer URL history is a painful consequence.  Could the URL history be retained between invocations?  I use a set of about a dozen different endpoints frequentl, so a history size of 12-20 would likely be enough.

It would be even better if the last used request header and/or body and/or type (POST/GET/..) and/or Protocol (HTTP/1.1 etc.) for each URL could also be saved but perhaps that is asking too much.

 Bless you for making this tool. 

Pending Review
Last Updated: 24 Jun 2019 20:58 by Eric

A simple change request: when I navigate, using Fiddler, to a page that has an untrusted https certificate, I get the popup from Fiddler warning me of the same. I want to get this popup, I don't want to disable it. However, when I click "Yes" on the popup, the main Fiddler window is brought into front, on top of my browser. My environment has a lot of self signed certificates in use on non-production systems, so this is happening quite often.

I propose the popup should work as now, but clicking on the popup should not bring the main Fiddler window up, in case it was minimized or under other windows.

Thanks a lot for your great work on the program.


Pending Review
Last Updated: 24 Jun 2019 20:56 by Eric

Hello Sir , 

            I've discovered the security bug which is Bypassing UAC in Fiddler Software . any reward or acknowledgement in bug report program ? 


Sai Wynn Myat. (@404death)

Pending Review
Last Updated: 17 Jun 2019 08:03 by ADMIN
Created by: Tom
Comments: 1
Type: Feature Request

Fiddler is great but the composer tab really needs some love. For example, it could do with text manipulation features from other applications - double click selects a chunk of text, but it doesn't appear to be aware of common symbols like : ? # " ' ; etc, instead it highlights up to the next space. If i were to do this in vs code or notepad++ it would be more intelligent about delimiters and highlight the portion before the : or inside the " ".


Pressing tab inside the editors moves to the next editor - this seems counter intuitive in this context as you'd expect the editor to insert a tab rather than move you to another field.


I've been using fiddler for years and this has always bugged me. I normally edit the request in another application and paste it in, but it'd be great if i could do some basic editing in fiddler itself. It shouldn't be full ide-mode, but a little bit of help would be appreciated.

Simple things that would make this much better:

  • Add a little syntax highlighting/validation (invalid json for example)
  • Autocomplete for known headers
  • Have the url box be expandable, so you can actually edit long requests
  • Intelligent selection based on delimiters or context



Pending Review
Last Updated: 07 Jun 2019 17:14 by Mason
Created by: Mason
Comments: 6
Type: Feature Request
In previous versions, it was possible to see the entire timestamp for a given session timer which would include the date.  In the latest version, it only shows the time (no date) and I can't find any configuration options that would allow a full timestamp.
Pending Review
Last Updated: 31 May 2019 11:43 by ADMIN
Created by: James
Comments: 3
Type: Bug Report

It's incredibly an annoying prompt that occurs every. single. time. i open up fiddler.


Check for updates behind the scenes if an update exists and only let me know when an update exists

Pending Review
Last Updated: 27 May 2019 05:49 by Vasilev

Running into more and more issues where the end user are authenticating via a smartcard. If the issue is after the initial handshake then we may be able to turn on Fiddler after the authentication and everything is okay. If the issue is specifically to do with the authentication or authentication screens then we are stuck and have no tool to use to debug the issue, especially when it may involve multiple processes. 

 With appropriate new settings in the Fiddler Options, could the socket connection on a TLS send certificate challenge call the appropriate API to use the SmartCard reader as well as challenge for a pin/biometric instead of reading from a certificate.cer file?  

Pending Review
Last Updated: 22 May 2019 20:35 by Jonathan
Created by: Jonathan
Comments: 3
Type: Bug Report


My windows DPI scaling is set to 200%, as my resolutions to 2000x3000.

If I load fiddler normally, I see the following blurry text.



So i saw this bug report, which suggested to load up fiddler with -dpiaware, and now some text is better, but most of the tabs and buttons are incorrect sizes in the composer. In my opinion its more usable with the blurry text. I also tried to change the Fiddler.exe.config - EnableWindowsFormsHighDpiAutoResizing from true to false, but the only affect this had was to change the size of the mouse cursor.


Any ideas on something else to try, or is this a limitation of Fiddler / .Net WinForms.

Pending Review
Last Updated: 15 May 2019 15:55 by Eric

I want to capture traffic from a Chrome Incognito window only.

When I click the 'pick target' button on the toolbar and point it at the Chrome window it picks up some particular process from chrome, but that does not seem to be the one from where network requests are sent from.

Looking at Chrome's Task Manager and comparing with what Fiddler shows, Fiddler is picking up the "Browser" process, while requests are coming from the "Utility: Network Service" process, thus the difference.

An acceptable solution for this would be if we could enter the process ID manually in the UI, instead of using the target picker.




Pending Review
Last Updated: 13 May 2019 15:58 by EricLaw


Websocket monitoring is such a cool feature in fiddler. What i´m missing is the possibility to export all messages sent and received via the websocket.

In Wireshark i would associate that functionality with "Follow TCP stream".


The reason behind:

I want to search within the websocket communication for certain id´s patterns etc. This is currently not possible as every message is handled separately in fiddler.

What i would expect:

Beeing able to export selected or all messages in the WebSocket pane. (one could think of adding "received","sent" and a timestamp between the messages with a certain beginning to be able to filter those messages later.)


I would call the fact that:

- "Save" - "Selected Sessions" "as Text or ZIP" is only saving the websocket HTTP upgrade request together with the response but without the websockets payload

 a bug.


Or i am missing something. Comments welcome...



Pending Review
Last Updated: 08 May 2019 15:11 by ADMIN
Created by: Emma
Comments: 1
Type: Feature Request
Please add python support to fiddler ,thanks.kepp it sample ,just sample is ok.
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