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!



Under Review
Last Updated: 22 Aug 2019 22:06 by Barna
Created by: Peter Wicks
Comments: 1
Type: Feature Request
Add support for Socks5 + Socks Proxy w/ Authentication
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.

Under Review
Last Updated: 20 Aug 2019 10:27 by Dogukan
Created by: Imported User
Comments: 3
Type: Feature Request
The error messages pops up on Windows 10 version 1703.  Fiddler installs and runs with not issues on Windows 10 version 1607.
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!

Last Updated: 09 Aug 2019 10:09 by ADMIN
This is a feature that's present in both the Firefox and Chrome dev tools, and it's incredibly useful. Fiddler is already great, and that would make it so much better :-)
Last Updated: 09 Aug 2019 10:08 by ADMIN
Created by: Shmuel
Comments: 2
Type: Feature Request
I find having Capture on when you start Fiddler a pain since almost always one of the first things I have to do is turn it off. I'd like the option to just have it off on startup.
Under Review
Last Updated: 31 Jul 2019 18:06 by ADMIN
Created by: Imported User
Comments: 3
Type: Feature Request
I had request with json body, after exporting to curl, looking at the batch file, i didn't see the body part of the request
Last Updated: 29 Jul 2019 08:56 by ADMIN
Created by: Imported User
Comments: 2
Type: Feature Request
When Fiddler generates a certificate based on the original server certificate (using oSession["X-UseCertCNFromServer"]), it doesn't include all ServerAltNames from the original certificate.
Last Updated: 16 Jul 2019 07:40 by ADMIN

Repro steps:

1. Inspect a websocket connections traffic

2. Expand the preview column so that the message body should show more than 65 characters.

3. Observe that even though the column is wide enough to support more than 65 characters, only 65 characters are displayed.

Last Updated: 10 Jul 2019 10:38 by ADMIN
WebSockets offer a mechanism for doing compression of messages. Fiddler's WebSocket Inspector should provide a simpler means of viewing such content.

The mechanism looks to be a simple DEFLATE operation:
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.

Last Updated: 04 Jul 2019 11:41 by Daniel


  • Have a list of several AutoResponder rules.

Steps to reproduce:

  • Select a rule in the list.
  • Press the M hotkey to set a comment for the rule.
  • Edit the comment.
  • Save the comment by confirming with OK.

Expected result:

  • The comment edit dialogue displays the current comment of the rule selected in the list.
  • Confirming the dialogue updates the comment of the rule selected in the list with the text box content.
  • The list selection does not change.

Actual result:

  • The comment edit dialogue displays the current comment of the rule selected in the list (expected).
  • As the edit dialogue opens, the selection in the AutoResponder list changes and a different rule is highlighted.
  • Confirming the dialogue updates the comment of the newly selected rule, not the one the user manually selected and whose initial comment was shown in the edit dialogue.

Version: 5.0.20192.25091 (2019-06-04)
Platform: Windows 10 build 17134, .NET 4.7.1

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?  

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