Compare Web Traffic

Compare two web sessions

  1. Select two sessions in the Web Sessions List.
  2. Right-click one of the sessions.
  3. Click Compare from the context menu.

By default, this will attempt to launch WinDiff or WinMerge to compare the traffic.


  • If you're using WinDiff, you can cause it to break each line on punctuation by holding ALT or SHIFT while clicking on the Compare menu item.
  • You can set the fiddler.differ.ultradiff preference to False if you don't want Fiddler Classic to attempt to reorganize the headers and URL for simpler diffing when saving the files.

Change default text comparison tool

  1. Click Tools > Options > Tools.
  2. Enter the location for the tool executable.

Set custom command-line arguments

In the QuickExec box:

  1. Provide the path to the tool:

    PREFS SET fiddler.config.path.differ "C:\Program Files (x86)\Microsoft Visual Studio 11.0\Common7\IDE\devenv.exe"
  2. Configure the command line to match what the tool expects:

    PREFS SET fiddler.differ.Params "/diff \"{0}\" \"{1}\""
  3. (Optional) Set an alternate command line that will be invoked if you hold ALT or SHIFT while invoking the comparison:

    PREFS SET fiddler.differ.ParamsAlt "/diff /binary \"{0}\" \"{1}\""

Compare multiple sessions at once

The Traffic Differ Extension allows you to compare multiple sessions at a time.

See Also

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