Pending Review
Last Updated: 18 Feb 2020 18:28 by TelerikHDMI
Created by: TelerikHDMI
Comments: 0
Type: Feature Request

I would be nice if Fiddler could decrypt zstandard compressed requests.

Pending Review
Last Updated: 14 Feb 2020 07:39 by George

It's a common practice to compress binary payloads inside WebSockets using zlib.deflate, though in Fiddler they are displayed as binary dump. It's quite simple to analyze two trailing bytes of a binary packet, and if they are equal to 0xFFFF you could try to apply zlib.inflate to that packet. If it succeeds, replace the binary contents with its unzipped text equivalent.

WMBR, George Hazan.

Pending Review
Last Updated: 06 Feb 2020 13:44 by ADMIN
Created by: S
Comments: 3
Type: Feature Request

It'd be extremely useful if Fiddler could have the ability to do filtering non-destructively, where filtering doesn't drop data/entries/lines altogether, but rather, merely hiding them from display.

This enables the ability for you to do multiple levels/layers/slices of filtering, as there's very often a need for doing on any given capture session. Currently, however, when you filter on something, the capture data gets dropped from the data/result set, lost altogether.

Process Monitor by Microsoft/Sysinternals has this ability, and it's extremely useful, allowing you to not only do layers of filtering, but also allowing the ability to traverse back up the "stack" 1..n filter layers, and if/when needed, able to un-filter all the way back up to baseline of all capture data shown (and without having to re-load a session save).

Procmon also has the ability to "Drop filtered events", which when enabled does destructive filtering, dropping any non-filter-matching packets from that point forward:

This would also be handy to have, but not crucial; much more beneficial/important is the ability to filter non-destructively.

Pending Review
Last Updated: 28 Jan 2020 00:47 by Eric
Created by: Michael
Comments: 1
Type: Feature Request

Viewing and editing query parameters is not a pleasant experience.

I'd prefer not having to switch to Postman for editing and sending requests, but its UI is currently so much better for this task.

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

Pending Review
Last Updated: 16 Dec 2019 19:51 by Eric




(Some blocking rules are not shown)


When I use the "filter now" function, it does not filter properly.

It goes like this:

Prior to this, I used the "Filters" feature, but there was always a link that was not blocked.(this url:  )

With the "Filters" function turned on, I used the "Filter now" function several times to block this link, but the result was only blocked at that time, and then came out again.

Now I turn off the "Filters" function, and then use "Filter now" to block that link. As a result, the blocking rule is not displayed in the lower left corner. Other blocking rules can be displayed normally.



Pending Review
Last Updated: 27 Nov 2019 08:15 by ADMIN
Hello! I have the latest version of the feedler, and the "Show only traffic from" function does not work in it. It happens that it intercepts the traffic of some tabs, but almost always not.
Pending Review
Last Updated: 14 Nov 2019 14:00 by ADMIN

Run 1 Example 1 (first 32 characters): {"SummaryTracker":null,"Column1

Run 2 Example 2 (first 32 characters):  ¢ €ªªªêÿteÐ(È„´47ó ¯*·:˜y@X


if (oSession.uriContains("/yadayada?Id=")) 
var qs = oSession.fullUrl.ToString;
var qsT = oSession.fullUrl.Split("=");
var qsone = qsT[1] + "_ABC";
oSession.SaveResponseBody("C:\\temp\\" + qsone + ".json");

Using latest Chrome as browser. Running fine for many months until 1 November 2019, Boom! Can anyone tell me what is going on? It appears to be random.


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: 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: 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: 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: 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.
Pending Review
Last Updated: 23 Apr 2019 15:22 by Eric

Reformatter.cs, around line 880, needs to support the new JavaScript feature of allowing underscores as (ignorable) digit separators. Otherwise, the parser treats _ as the end of the numeric value which breaks reformatting.



1 2 3