Need More Info
Last Updated: 06 Aug 2020 13:46 by Eric

I recently am having an issue with MS Teams while running fiddler.  MS Teams keeps giving disconnect errors. That's when I noticed that fiddler it proxying it's traffic even though I have filters set to "Show only the following Hosts", and are not included in the hosts.  I also notice other items in my sessions list that are not in my list of hosts so what is going on?

I don't really want to post my list of hosts publicly.  If you need them, please let me know and maybe I can email them to someone.


Pending Review
Last Updated: 29 Jul 2020 12:52 by Eric
Created by: li
Comments: 1
Type: Bug Report

Hi,I have a problem,and I need your help,thankyou.

    when I click "Rules" -> "Customize Rules", pop up a prompt: Urhandled exception has occurred in your spplication. If you click Continue, the application will ignore this error and attempt to continue. If you click Quit, the application will close immedi ately.Font Cowrier New' does not support style 'Regular' .

  【My computer system is  windows7 64】

Last Updated: 21 Jul 2020 15:31 by Eric

When loading the SAZ file, the requests are ordered incrementally based on the order they were saved in.

For example, a Fiddler session was sorted by URL and then saved to SAZ. When the file is loaded, the requests are still sorted by URL but the original index numbers are lost and the requests are numbered incrementally as per this sort. This means that it is not possible to sort the session back to the original linear order by clicking on the index column (#) as it was possible to do before the save/load.

I've seen that the original index is saved in the Comments column. This is only a partial solution because:

1. When sorting by this column, a lexical sort is performed meaning the sessions would be numbered: 1,10,100,101,11,12..19,2,20,21 etc...
2. If the request had a comment associated with it, this overrides this feature and the original index number is lost.

Also, I know it's possible to sort by ClientDoneRequest as a good approximation but it obviously doesn't recreate the original order.

It would be beneficial to keep the original index numbers (even including the gaps between them) as there is information there that shouldn't be lost when saving.


As always thank you for your work on this wonderful product.







Last Updated: 17 Jul 2020 10:42 by ADMIN
Created by: Sergey
Comments: 2
Type: Bug Report

Hello, we have found the issue on the v5.0.20202.18177 for .NET 4.6.1 the session data could be copied only using hot keys.


but only session url is saved when I try to Copy session by clicking on the menu item.

Last Updated: 07 Jul 2020 10:29 by Ruben Brito

I couild highlight a row in the captured data and hit the context menu for Copy | Session and it would copy the data and present it in this type of format when pasted into notepad:



Accept-Language: en-US; q=1.0, en; q=0.9
X-SignalR-Id: f83b9717-2553-438f-b76c-4c3e70159a39
Authorization: Bearer eyJhbGciOiJSUzI1NiIsImtpZCI6IjQyRjIzMDlCQzZGMkNFQzNBQzc1MTA3RUQyRTFCREE4NzEwQUI5MUIiLCJ0eXAiOiJKV1QiLCJ4NXQiOiJRdkl3bThieXpzT3NkUkItMHVHOXFIRUt1UnMifQ.eyJBY3R1YWxVc2VySWQiOiIxIiwiQXV0aFRva2VuSWQiOiI2OTdlZDkzOC05YTY1LTQyZDctODI2MS04MGRiYzhkYTE1OWQiLCJyc3RzOnN0czpjbGFpbXM6dXNlcjp1c2VySWQiOiIxIiwidXBuIjoiU3VwZXIiLCJhdXRobWV0aG9kIjoibG9jYWw6cHdkIiwibmFtZWlkIjoiU3VwZXIiLCJuYmYiOjE1ODc0OTI1MzMsImV4cCI6MTU4NzU3ODkzMywiaWF0IjoxNTg3NDkyNTMzLCJpc3MiOiJ1cm46dG9rZW5hdXRoZW50aWNhdGlvbnByb3ZpZGVyOlNBRkVHVUFSRF9BUFBMSUFOQ0UifQ.Leqmwi7cbogsB_XYv9DpJ2SCgCtkl7WsY8Y6pXjfHVSm1P9-82ayeNK_J9rmQUdqZrWjmCeK4DxiyifKAzpgCJm5y0XgUX02jJ5RiD_i8EWOT6ywyxgRRKLefm36jHsWVavLpidJMo4QyOEUGX1OHw0-Cgv2kJyESwkNYLgVQB34WEGMSe2Sh1kVkQrVl-WwcmlckL7yw5rPaofje5lEXrbGMHbNTfBAuei08DVf49DBjV7FGZWRMpvB3mIpWqAZylTXu2DNcfol2ZuVYG1PmTY7pENZGzO98gT7c08Q6wqbZF1846F47oZ2wZXrcYRHkNO8nJ6N7JUN8koGMQ2P6g

HTTP/1.1 200 OK
Cache-Control: no-store, must-revalidate, no-cache
Content-Length: 1872
Content-Type: application/json; charset=utf-8
Content-Language: en-US
Vary: Origin
X-Frame-Options: DENY
X-Content-Type-Options: nosniff
Strict-Transport-Security: max-age=31536000; includeSubDomains
X-XSS-Protection: 1; mode=block
Content-Security-Policy: object-src 'none'; img-src 'self' data:; font-src 'self'
Referrer-Policy: same-origin
X-Cluster-Role: primary
X-TokenLifetimeRemaining: 1433
Date: Tue, 21 Apr 2020 18:16:29 GMT

[{"DiscoveredDate":"2020-04-21T17:20:10.228Z","AccountName":"BobAdmin","AccountDomainName":null,"AccountId":10,"AssetName":"PAM-QA-WIN2019","AssetId":23,"AssetPartitionId":1,"AssetPartitionName":"Import","SshKeyProfileId":1,"SshKeyProfileName":"Import SSH Key Profile","SshKeyDiscoveryScheduleId":15,"SshKeyDiscoveryScheduleName":"Import SSH Key Discovery","PublicKey":"AAAAB3NzaC1yc2EAAAADAQABAAABAQCjJh0+dkm7SMIzhCVPaZTxu0pQA9uhScH26GSxDb5ddoYigi9dlq45/4zal230Nk4o3IQmbP7hLikKTCr2Y3GRUZJEJ8IdQe9zXtGnm+N2iczbmg9kGPcb6j3pMcfxrjZlcOFOXgRaz1tnJXdaSLuM4kI45+sJjtdJ9e/nDdX1HgWVyo0U3CO7q/k/srI1+KaetKW58iCIK6zZnoW8jUhmyXdxA/UkkOwUCdK7kQwOn6kBV7pRgErS1nWmd4RZ7UNi0iSpZdrg6yL7mngLfzS7ee4iZ2Hp3WUY8s1aYhPkDJcJl6uEbxy2NpwLvbUgCWcbJCUPRQUKAdheR7uJuTfF","Comment":"bross@prod@Q3LJ2RQ2","Fingerprint":"4D7280929A77CAD8C0EF03099AF90F4F","KeyType":"Rsa","Options":null,"KeyLength":2048,"AccountStatus":"Managed","IsIgnored":false,"IsManaged":true},{"DiscoveredDate":"2020-04-21T17:20:09.686Z","AccountName":"BobAdmin","AccountDomainName":null,"AccountId":10,"AssetName":"PAM-QA-WIN2019","AssetId":23,"AssetPartitionId":1,"AssetPartitionName":"Import","SshKeyProfileId":1,"SshKeyProfileName":"Import SSH Key Profile","SshKeyDiscoveryScheduleId":15,"SshKeyDiscoveryScheduleName":"Import SSH Key Discovery","PublicKey":"AAAAB3NzaC1yc2EAAAADAQABAAABAQDP1WLHVC8mq6ICGre8OUPi5FQMYxomTGlSgnVqIvIUHLNI8PPH0xpkOpfhlZASzu7WtHWX37LDvEcUqW0gYb0eYww56IeERHui5yuJ7ocJnXETO33W+n0pnYjZuyqxEjSa8P14O6smg5z6bxm+/StItb8GyL1kBdQdoVeVMfWUSUO/2qyvmK22QOS8df2Gl+MWcBvsoU6rrtTq5N9FlS05zFsQJGUt/MrV3qHhKUqviFEZ1sl5ziisRknWInCb+YTkq7a5HFSbSAjxHZDjwPJ92gTWs+W/n6GsSY9Xjnjx+rFfpD1bSD4JnjwJ2QUsbTLPutJ0CpLFdOUJbgzsQY1N","Comment":"Safeguard_Windows_SSH","Fingerprint":"850585DBE61DE4F2D638EC3DE66CCE83","KeyType":"Rsa","Options":null,"KeyLength":2048,"AccountStatus":"Managed","IsIgnored":false,"IsManaged":false}]


Now all I get is the URL...

Last Updated: 24 Jun 2020 12:30 by ADMIN

Removing interception certificates via Fiddler options "Remove Interception Certificates" only removes them from Personal and Trusted Root Certification Authorities of the Local Computer Store.

Certificates located in Current User Store - Trusted Root Certification Authorities  and Intermediate Certificates is not removed.

This certificate is not trusted after using "Remove Interception Certificates" and has status "This CA Root certificate is not trusted because it is not in the Trusted Root Certification Authorities store".

sigcheck -t[u]v doesn't show any warnings.

Tested this on both Windows 7 and 10.

Tried refreshing certmgr, restarting it, and rebooting machine with no success - certificates are still there.

This should


Last Updated: 22 Jun 2020 07:13 by Tony


I updated Fiddler to v5.0.20202.18177

Progress Telerik Fiddler Web Debugger

v5.0.20202.18177 for .NET 4.6.1
Built: mardi 14 avril 2020

64-bit AMD64, VM: 37,0mb, WS: 65,0mb
.NET 4.8 WinNT 10.0.18362.0

You've run Progress Telerik Fiddler: 17 times.

Running on: xxxx:8888
Listening to: All Adapters
Gateway: No Gateway

Copyright ©2003-2020 Progress Software Corporation. All rights reserved.and started to get error at launch

then i started to get error at launch : Failed to register Fiddler as the system proxy

I found a possible solution : change "WinHttp Web Proxy Auto-Discovery Service" startup to automatic

a reboot later, Fiddler worked fine 

but today, the error is back

i checked, the service is still in automatic startup


So i get a previous installer, and installed a previous version and the error is gone

Tried to update again, the error come back, rollbacked to previous version, working again

Progress Telerik Fiddler Web Debugger

v5.0.20182.28034 for .NET 4.6.1
Built: mercredi 27 juin 2018

64-bit AMD64, VM: 62,0mb, WS: 118,0mb
.NET 4.7.1 WinNT 10.0.18362.0

You've run Progress Telerik Fiddler: 18 times.

Running on: xxxx:8888
Listening to: All Adapters
Gateway: Auto-Config

Copyright ©2003-2018 Telerik EAD. All rights reserved.

Didn't found any thread on the forum about this issue

Last Updated: 17 Jun 2020 08:19 by ADMIN
Created by: Tony
Comments: 1
Type: Bug Report


When i started latest version of Fiddler, i started to get an error window at launch saying "Failed to register Fiddler as the system proxy"

But as usual, i have plenty opened windows at the same time.

While i'm doing a search for a solution, Fiddler and the error window goes to background.

But when i come back to Fiddler, i'm unable to exit the application.

The error windows is not referenced in the taskbar and it's a pain to find it.

The best solution is to go to desktop "Win+D" and focus on Fiddler to get the splash screen and the error window visible again.

Once the error window closed, i can close Fiddler.

The issue is the error window staying on background and not having an entry in taskbar.

Last Updated: 11 Jun 2020 10:20 by ADMIN
Last Updated: 27 May 2020 07:39 by ADMIN

Just installed on Windows 10 Version 1909 OS 18363.836.  Hangs whenever I try to do Step 1 of the docs, set decryption.  Debugged in VS 2019, access violation trying to read 0x00000, NullException.  Finally, shutdown all of my work and restarted machine.  Error cleared and this time asked me to accept the new Cert.  

What a terrible first time experience.  Issue resolved.

Pending Review
Last Updated: 22 May 2020 00:07 by Robin
Created by: Robin
Comments: 2
Type: Bug Report

Using iOS 13.4.1

Using Catalina 10.15.4

Using Fiddler for Mac

I have followed this blog post for configuration. 

But when I try to go to the http://ip4v.fiddler:8888 I get the below error

[Fiddler] DNS Lookup for "ip4v.fiddler" failed. System.Net.SocketExceptionFactory+ExtendedSocketException Device not configured


Last Updated: 15 May 2020 18:44 by ADMIN
Last Updated: 28 Apr 2020 13:50 by ADMIN

Date of update appears as 04/21/2019, should be 04/21/2020:

5.0.20202.18177 [04/21/2019]
 "Accept all CONNECTs" option in AutoResponder
Last Updated: 27 Apr 2020 20:00 by ADMIN
Created by: Eric
Comments: 2
Type: Bug Report


Set Examine to "Headers Only"

OBSERVE: "Search binaries" and "Decode First" checkboxes are correctly disabled.

Perform a search


OBSERVE: BUG: When the dialog reopens, the "Search Binaries" checkbox is not disabled.


The bug is in the initialization of the dialog. The selected entries in the comboboxes for "Examine" and "Search In" are set in that order, but the code in the SelectedIndexChanged event handlers is not independent. The SearchIn combobox's change handler sets the state of SearchBinaries checkbox without considering the state of the Examine combobox.

Last Updated: 27 Jan 2020 15:53 by ADMIN

Some third-party libraries, for example HtmlAgilityPack, cannot be added as references to FiddlerScript.

The path to the assembly is added in the Tools -> Options -> Scripting -> References, but an error message that the assembly cannot be loaded appears when the method using the assembly is invoked.

Workaround: use JScript.NET as a scripting language.

Pending Review
Last Updated: 06 Jan 2020 16:21 by Eric

Fiddler UI mnuSessionContext "Inspect in New Window",which method of fiddler call?

I didn't find the corresponding call method in the fiddlecore document.

Please @Eric