AutoResponder Reference

Fiddler's AutoResponder tab allows you to return files from your local disk instead of transmitting the request to the server.

On the AutoResponder tab, you enter a match string and an action string, and Fiddler will undertake the action if the request URI matches the match string.

You can also Import a .SAZ file to enable playback of previously captured traffic, or drag-drop sessions from the session list to replay previous responses.

Keyboard Hints

Hit the Plus key to promote a rule to earlier in the list
Hit the Minus key to demote a rule to later in the list

String Literals

Fiddler will match string literals (case insensitively)

Rule	Matches
*	http://www.example.com/Path1/query=example
EXAMPLE	http://www.example.com/Path1/query=example
path1/	http://www.example.com/Path1/query=example
query	http://www.example.com/Path1/q=Query

Exact Match

Fiddler supports an exact, case-sensitive match syntax for expressions which begin with exact:

Rule	Matches
EXACT:http://www.example.com/path	http://www.example.com/path
EXACT:http://www.example.com/path	http://www.example.com/Path (No Match - mismatched case)
EXACT:http://www.example.com/path	http://www.example.com/path/q=Query (No Match - substring different)

Regular Expressions

Fiddler supports regular expression syntax for expressions which begin with regex:

Rule	Matches
regex:.*	http://www.example.com/Path1/query=example
regex:.*\.jpg	http://www.example.com/Path1/query=foo.jpg&bar http://www.example.com/Path1/query=example.jpg
regex:.*\.jpg$	http://www.example.com/Path1/query=foo.jpg&bar (No Match - improper ending) http://www.example.com/Path1/query=example.jpg
regex:.*\.(jpg\|gif\|bmp)$	http://www.example.com/Path1/query=foo.bmp&bar (No Match - improper ending) http://www.example.com/Path1/query=example.gif http://www.example.com/Path1/query=example.Gif (No Match - mismatched case) http://www.example.com/Path1/query=example.bmp
regex:(?insx).*\.(jpg\|gif\|bmp)$	http://www.example.com/Path1/query=foo.bmp&bar (No Match - improper ending) http://www.example.com/Path1/query=example.gif http://www.example.com/Path1/query=example.Gif http://www.example.com/Path1/query=example.bmp
	Got a great regular expression to share? Please send it to me using the "Contact" link at the top-right side of this page!

You can learn more about regular expressions here.

You can specify regular expression options (like case-sensitivity) by leading the expression with an appropriate declaration. (?insx) works well; it turns on case-insensitivity, requires explicit capture groups, enables single-line syntax, and enables comments after the #character. Learn more on MSDN.

Beyond returning files, you can also perform a few other special actions...

Action String	Result...
filename	Return filename as server's response
*bpu	Break on request before hitting server
*bpafter	Hit server, but break on the response