Last Updated: 18 Nov 2020 15:26 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: 16 Nov 2020 08:24 by ADMIN

This bug occurs in both Fiddler and Fiddler Everywhere so you may want to take a look.

The system I'm running on is Win7x64 with latest patches loaded.

Note that when Fiddler/Fiddler Everywhere is not loaded, I can access this website normally.

====== Message from Fiddler v5.0.20204.45441 for .NET v4.6.1 Built: 2020-11-03 ======
HTTP/1.1 200 Connection Established
FiddlerGateway: Direct
StartTime: 10:19:31.203
Connection: close

fiddler.network.https> HTTPS handshake to devblogs.microsoft.com (for #14) failed. System.Security.Authentication.AuthenticationException 呼叫 SSPI 失敗,請查看內部例外狀況。 < 接收到的訊息超出預期或格式不正確。

Win32 (SChannel) Native Error Code: 0x80090326

====== Message from Fiddler Everywhere 1.2.1 Built: Friday, November 6, 2020 ======
fiddler.network.https> HTTPS handshake to devblogs.microsoft.com (for #17) failed. System.Security.Authentication.AuthenticationException Authentication failed, see inner exception. < 接收到的訊息超出預期或格式不正確。

Win32 (SChannel) Native Error Code: 0x80090326
Last Updated: 23 Oct 2020 13:03 by Mark DeMichele

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 teams.microsoft.com 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.


Last Updated: 12 Oct 2020 05:24 by ADMIN

Fiddler’s “Auth” Inspector uses Encoding.Default() for decoding base64-encoded BASIC auth credentials. This was common practice at the time this was first written but is now obsolete. https://tools.ietf.org/html/rfc7617, written much later, demands UTF-8.

Chromium and Firefox encodes credentials using UTF-8.


Last Updated: 05 Oct 2020 04:51 by ADMIN

Hi everyone.


A screenshot of the error is provided, I think there are extra characters in the form, these should not appear, it seems to be caused by a decoding error. Note that the transfer method "transfer-encoding: chunked".


Last Updated: 28 Sep 2020 05:13 by ADMIN

If the user configures a list of sites inside Tools > Options > HTTPS > "Skip Decryption for hosts", this configuration list is ignored if the AutoResponder is enabled with the "Accept all connects" checkbox ticked.

This should be fixed because otherwise it's extremely difficult to figure out what's going wrong.


Incidentally, this behavior might be responsible for this issue: https://feedback.telerik.com/fiddler/1479071-fiddler-refusing-to-ignore-teams-microsoft-com-and-is-causing-my-ms-teams-app-on-windows-to-break

Last Updated: 02 Sep 2020 10:28 by ADMIN


I've the following request response:

    "proId": 98767975948505330

This is correctly displayed in the "Raw Tab", but when switching to the JSON tab, the displayed number is not correct.


Could you fix this ?


Last Updated: 26 Aug 2020 18:17 by Jeff

"Target Any Process" feature no longer working with Chrome. It used to work but no longer works specifically with Chrome. Still works with other processes. Capturing still works with Chrome as long as I am not using the "Target Any Process" feature.

Last Updated: 20 Aug 2020 15:20 by Lutz

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:


PUT https://xxx.xxx.xxx.xxx/service/core/v3/AssetPartitions/-1/DiscoveryJobs/29 HTTP/1.1

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: 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.

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.

Last Updated: 10 Dec 2019 07:27 by ADMIN

When HTTPS decryption is enabled in Fiddler, Fiddler parses the ClientHello and ServerHello HTTPS messages to determine the supported ciphers and other information, including TLS Extensions.

Unfortunately, Fiddler's HTTPSMessages parsers have a bug whereby if the extensions are larger than the available data on the stream/pipe, reading of the extensions is skipped and misleading text suggesting that no extensions were sent is shown in the Inspectors. For instance, the current version of Chrome Canary sends ~1308 bytes of TLS extensions in the ClientHello, but only 908 bytes are available at the time that the message is read. Fiddler claims that the ClientHello contained no extensions. 

Instead of performing a single .Read() call and ignoring the result if the size is less than expected, Fiddler should continue to read the stream until the promised number of bytes have been read.


[This issue is similar to https://crbug.com/1028602#c2, although the implementation is obviously unrelated).

Last Updated: 03 Dec 2019 21:23 by Wojciech Rajchel
Created by: Wojciech Rajchel
Comments: 2
Type: Bug Report

Describe the bug
After following the steps in the Capture All IIS Traffic on the Web Server Forum Post Fiddler goes into an endless loop.


To Reproduce
Steps to reproduce the behavior:

  1. Disable the firewall on the IIS Web Server

  2. Edit machine.config proxy settings to point to

            <proxy autoDetect="false" bypassonlocal="false" proxyaddress="" usesystemdefault="false" />
  3. Set the WinHTTP Proxy Settings to point to
    netsh winhttp set proxy

  4. Change the IIS Site Bindings to an alternate Port. In this example, it is 8080
    IIS Bindings

  5. In Fiddler, execute !listen 80 in QuickExec
    Fiddler QuickExec

  6. Add Custom Rule to Forward Requests Received to WinHTTP Port. In this case, 8080

    static function OnBeforeRequest(oSession: Session) {
        // ...Code removed for brevity...
        if(oSession.host == "[INSERT_HOST_NAME_HERE].com:80")
            oSession.host = "[INSERT_HOST_NAME_HERE].com:8080"  /// This is the Fiddler Port
        // ...Code removed for brevity...    

Expected behavior
Fiddler should capture all traffic to and from the web server. This configuration should configure Fiddler as both the normal proxy and reverse proxy simultaneously.

Desktop (please complete the following information):

  • OS: Windows Server 2012 R2
  • Browser: Any
  • Version: Any
Last Updated: 14 Nov 2019 15:40 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] 

Last Updated: 06 Nov 2019 01:28 by S
Scheduled for Fiddler for Windows vNext

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.

Last Updated: 23 Oct 2019 07:28 by ADMIN
Scheduled for Fiddler for Windows vNext

Describe the bug
"Get Started" tab resizes badly when the font size is increased, making headings like "Start", "Recent" invisible or with vertically arranged letters.

To Reproduce
Steps to reproduce the behavior:

  1. Change font size to 14 from Tools -> Options -> Appearance -> Font Size
  2. Limit the space available for the tabs by moving the vertical splitter to the right
  3. The text in the headings starts to layout vertically

Expected behavior
Get Started should look good on all available font sizes and Windows scaling settings.


  • Version 5.0.20194.41348
1 2