Composer (formerly "Request Builder")

The Composer allows you to craft custom requests to send to a server. You can either create a new request manually, or you can drag and drop a session from the Web Sessions list to create a new request based on the existing request.

Modes

There are two modes for the Composer. In Parsed mode, you can use the boxes to build up a HTTP(S) request. In Raw mode, you must type in a properly formatted HTTP request yourself. Generally, using Parsed Mode is what you want.

Options

The Options tab exposes options that allow you to customize the behavior of the Composer.

Inspect Session selects the new session and activates the Inspectors tab when the request is issued.
Fix Content-Length Header adjusts the value of the Content-Length request header (if present) to match the size of the request body.
Follow Redirects causes a HTTP/3xx redirect to trigger a new request, if possible. The Composer will follow up to fiddler.composer.followredirects.max default redirections.
Automatically Authenticate causes Fiddler to automatically respond to HTTP/401 and HTTP/407 challenges that use NTLM or Negotiate protocols using the current user's Windows credentials.

Tips and Tricks

Use drag-and-drop from the Session List to create a new request based on a previously-captured request.

Use a # character in the RequestURL to be prompted for a series of sequentially-numbered URLs to download. If you enter a leading 0 (zero) before the "Start At" value, then all numbers will be padded with leading zeros (if necessary) to get to that width.

For instance, if you have the URL http://www.example.com/#/?a=#, and enter the Start At value as 08 and the End At value as 11, the Composer will request the following URLs:

    http://www.example.com/08/?a=08
    http://www.example.com/09/?a=09
    http://www.example.com/10/?a=10
    http://www.example.com/11/?a=11
Shift+Click the Execute button to immediately break the new request for further editing using Fiddler's Inspectors (added in v2.3.3.1).