Need More Info
Last Updated: 24 Dec 2023 03:00 by Eric

good morning 

i got error while capturing my app to

=== Windows 10 64bit OS==

===Protocols I have enabled: <client>;ssl2;ssl3;tls1.0;tls1.1;tls1.2

====== Message from Fiddler v5.0.20211.51073  for .NET v4.6.1
HTTP/1.1 200 Connection Established
FiddlerGateway: Direct
Connection: close> HTTPS handshake to (for #17) failed. System.Security.Authentication.AuthenticationException A call to SSPI failed, see inner exception. < The message received was unexpected or badly formatted

Win32 (SChannel) Native Error Code: 0x80090326


Any help ??

Thank you


The fiddler response

A SSLv3-compatible ClientHello handshake was found. Fiddler extracted the parameters below.

Version: 3.3 (TLS/1.2)
Random: 65 58 47 1D 28 AB A2 68 50 33 C7 75 1E A4 8B F5 9D A6 FB A0 F9 D2 54 FA 93 D5 AE 78 E5 26 7D 89
"Time": 26/07/1985 15:35:49
SessionID: empty
status_request OCSP - Implicit Responder
supported_groups x25519 [0x1d], secp256r1 [0x17], secp384r1 [0x18]
ec_point_formats uncompressed [0x0]
signature_algs rsa_pss_rsae_sha256, rsa_pss_rsae_sha384, rsa_pss_rsae_sha512, rsa_pkcs1_sha256, rsa_pkcs1_sha384, rsa_pkcs1_sha1, ecdsa_secp256r1_sha256, ecdsa_secp384r1_sha384, ecdsa_sha1, dsa_sha1, rsa_pkcs1_sha512, ecdsa_secp521r1_sha512
SessionTicket empty
ALPN http/1.1
extended_master_secret empty
renegotiation_info 00


Need More Info
Last Updated: 01 Nov 2023 15:00 by ADMIN

Help menu to check for updates says:

Error retrieving version information

System.IO.InvalidDataException ... Server Resonse Code = 502
    at [encoding error] ...Updater.cs:Line 90

GET /UpdateCheck.aspx?isBeta=False HTTP/1.1 Result 502


v5.0.20211.51073 for .NET 4.6.1
Built: Wednesday, December 15, 2021
64-bit AMD64, VM: 84.0mb, WS: 129.0mb
.NET 4.8 WinNT 10.0.19045.0
Need More Info
Last Updated: 27 Oct 2023 05:48 by ADMIN
I am looking for a way to display the times reported in a trace either as-is or convert to GMT and not the current TZ, without having to change the TZ setting of my own computer. I get far too many traces from all over the world and having the reported time display as it was recorded makes it much easier when I am assembling a report. 
Need More Info
Last Updated: 12 Jul 2023 07:10 by Xiaoming

I am trying to use settings Tools -> Win8 Loopback Exemptions -> Exempt All -> Save Changes. But it is giving me some error and saving those changes. Following is the error.

Failed to set IsolationExempt AppContainers; call returned 0x57

I am blocked due to this error and cannot perform tests on my application. Pls help.


Need More Info
Last Updated: 05 May 2023 07:09 by ADMIN
Created by: Michael
Comments: 1
Type: Bug Report

Fiddler would NOT allow me to save the file.  We tried this multiple times to various file locations. 

I do not have Visual Studio installed on my PC -- so I selected the latest verison in this form because it is a REQUIRED field. 

Fiddler provided the text below. 



Awww, Fiddlesticks!


Fiddler has encountered an unexpected problem. If you believe this is a bug in Fiddler, please copy this message by hitting CTRL+C, and submit a bug report at


Could not find file 'C:\Users\629243897\Documents\IBMSPend on v85 debug - 2 refreshes after logon.saz'.


Type: System.IO.FileNotFoundException

Source: mscorlib

   at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)


   at System.IO.FileInfo.get_Length()


   at Fiddler.frmViewer.actSaveSessionArchive(String , String
, Session[] ) in C:\Jenkins\Fiddler_Windows\workspace\Fiddler2\Fiddler.Shared\Viewer.cs:line 6808



Fiddler v5.0.20211.51073 (x64 AMD64) [.NET 4.0.30319.42000 on Microsoft Windows NT 10.0.22621.0]




Need More Info
Last Updated: 06 May 2022 11:37 by zaaz
Created by: jeriko
Comments: 2
Type: Feature Request

For now fiddler just have filter, and it not ignore traffic. Filter just hiding it.

Also Fiddler have option "Capture/Dont capture traffic" via menu File or F12. but it general for all. Also this option NOT work while the target app still use fiddler proxy.

My example problem :

I am using Nox to test MyDownloader app, while apk connect internet or requesting web data its ok to proxified by fiddler. But when I start downloading, the file is downloaded first to Fiddler cache until complete. after complete then fiddler continue request with that file response. That the problem. This also applied to all request in my PC. No problem if size just 20MB. But above 100M, 500MB, 1GB, sometime it make fiddler hang.

Also when i download file, then cancel it, fiddler still download file until complete. So to cancel that in fiddler, i need to disconnect it first.


For now, to bypass my problem i also using Proxi*fi*er filter to selecting mimetype.


Need More Info
Last Updated: 07 Apr 2022 05:55 by ADMIN

I've tried multiple allocation ratios and nothing solves the problem, the screen allocation ratio is 2560x1600.

Version Windows 10 Home Chinese
Version number 21H1
Installation Date ‎2021/‎12/‎25
OS Build 19043.1586
Experience Windows Feature Experience Pack 120.2212.4170.0

fiddler version :

v5.0.20211.51073 for .NET 4.6.1
Need More Info
Last Updated: 07 Mar 2022 10:17 by ADMIN


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!



Need More Info
Last Updated: 04 Jun 2021 07:02 by ADMIN
I ran Fiddler Classic on a remote PC via Windows Remote Desktop (RDP) on my laptop, which used an external large monitor for display. Both my laptop and the remote PC run Windows 10 OS. If somehow the remote desktop connection was temporarily lost (due to laptop going sleep or network glitch) and reconnected later, the Fiddler on the remote PC stopped responding to the mouse operation.
Need More Info
Last Updated: 08 Apr 2021 13:29 by ADMIN
Created by: Anton
Comments: 4
Type: Bug Report

Fiddler version: v5.0.20204.45441

If Fiddler is left for some time to work unattended then its memory usage is constantly growing.

I usually use Fiddler with some Autoresponder rules enabled and "Unmatched requests passthrough" option switched on. If left in this state for several hours an amount memory it uses could grow up to 10GB and even more which is quite annoying...

Autosave option is enabled and sessions are dumped every 5 minutes. So this behaviour is not because of session list is becoming large, it is being cleaned every 5 minutes.

Need More Info
Last Updated: 17 Feb 2021 09:31 by ADMIN

I've been trying to install the root certificate to decript https traffic with no results.


20:42:38:5197 Fiddler Running...
20:42:38:5202 Fiddler.Network.AutoProxy> AutoProxy Detection failed.
20:42:38:5202 AutoProxy failed. Disabling for this network.
20:42:38:5481 Windows 8+ AppContainer isolation feature detected.
20:42:44:4729 Assembly 'C:\Users\Mauro\AppData\Local\Programs\Fiddler\CertMaker.dll' was not found. Using default Certificate Generator.
20:42:44:4754 /Fiddler.CertMaker> Using .‰+˜ for certificate generation; UseWildcards=True.
20:42:46:0206 /Fiddler.CertMaker> Root Certificate located; private key in container '4f42d4e82d7f6c170e7a049cf6dfeeaa_8bf41fe8-e204-441e-8fc2-475cb85c8829'
20:42:48:8545 !Fiddler.CertMaker> Unable to auto-trust root: System.Security.Cryptography.CryptographicException: Access is denied.

   at System.Security.Cryptography.X509Certificates.X509Store.Add(X509Certificate2 certificate)
   at .‰.TrustRootCertificate() in C:\Jenkins\Fiddler_Windows\workspace\FiddlerCore\FiddlerCore.Shared\Common\Core\DefaultCertProvider.cs:line 965
Need More Info
Last Updated: 06 Dec 2020 06:31 by Eric

Hello dear fiddler support.


The bug i've found is: Fiddler doesn't support some encryption ciphers.


Recently I was trying to connect to site with "Decrypt SSL traffic" option set in fiddler to my genuine surprise i couldn't even connect to site.

I am using chrome 87.0.4280.88 64bit  and fiddler v5.0.20204.45441 for .NET 4.6.1

Without  "Decrypt SSL traffic" option set in Fiddler - chrome works fine.


So i decided to investigate what actually happen.

I run to site to check supported ciphers - here you can check it

and tried to reproduce the issue with wirshark  on.


In wire shark i can see that there is no ciphers supported by site 

Cipher Suites (24 suites)
    Cipher Suite: TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384 (0xc028)
    Cipher Suite: TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256 (0xc027)
    Cipher Suite: TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA (0xc014)
    Cipher Suite: TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA (0xc013)
    Cipher Suite: TLS_DHE_RSA_WITH_AES_256_GCM_SHA384 (0x009f)
    Cipher Suite: TLS_DHE_RSA_WITH_AES_128_GCM_SHA256 (0x009e)
    Cipher Suite: TLS_RSA_WITH_AES_256_GCM_SHA384 (0x009d)
    Cipher Suite: TLS_RSA_WITH_AES_128_GCM_SHA256 (0x009c)
    Cipher Suite: TLS_RSA_WITH_AES_256_CBC_SHA256 (0x003d)
    Cipher Suite: TLS_RSA_WITH_AES_128_CBC_SHA256 (0x003c)
    Cipher Suite: TLS_RSA_WITH_AES_256_CBC_SHA (0x0035)
    Cipher Suite: TLS_RSA_WITH_AES_128_CBC_SHA (0x002f)
    Cipher Suite: TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384 (0xc02c)
    Cipher Suite: TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 (0xc02b)
    Cipher Suite: TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA384 (0xc024)
    Cipher Suite: TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256 (0xc023)
    Cipher Suite: TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA (0xc00a)
    Cipher Suite: TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA (0xc009)
    Cipher Suite: TLS_DHE_DSS_WITH_AES_256_CBC_SHA256 (0x006a)
    Cipher Suite: TLS_DHE_DSS_WITH_AES_128_CBC_SHA256 (0x0040)
    Cipher Suite: TLS_DHE_DSS_WITH_AES_256_CBC_SHA (0x0038)
    Cipher Suite: TLS_DHE_DSS_WITH_AES_128_CBC_SHA (0x0032)
    Cipher Suite: TLS_RSA_WITH_3DES_EDE_CBC_SHA (0x000a)
    Cipher Suite: TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA (0x0013)


Now i now what the issue is about.

My question is how to fix the problem with ciphers.

In my opinion you should somehow add it in Fiddler.





Need More Info
Last Updated: 02 Nov 2020 13:02 by ADMIN


I'm testing a website that has a self signed SSL cert. I can navigate to this URL via an extra warning step on chrome (see attached screen shot).

However via Fiddler, I just get an error that "this site cannot be reached" and I can see it's dropped on the Fiddler side: I can see the tunnel CONNECT request, but no subsequent request.

I've enabled the option "Ignore server certificate errors (unsafe)" and restarted Fiddler, but the problem still persists.


As always, thank you for your work on this.



Need More Info
Last Updated: 05 Oct 2020 05:22 by ADMIN
Created by: S
Comments: 1
Type: Bug Report

When using Fiddler, there seems to be some bugs around resizing the GUI/UI, namely the dividers between sections such as between packet list vs. inspectors panes. It seems that when Fiddler is maximized full-screen, the divider (while using "Wide" layout) is shifted all the way up high, just beneath the initial packet in the list (Fiddler's update check).

I've been able to adjust the UI by manually manipulating Fiddler's registry settings, but even then it still seems finicky -- sometimes they take, sometimes they don't.

v5.0.20202.18177 for .NET 4.6.1
Built: Tuesday, April 14, 2020