How to use Fiddler ?

Fiddler is a free and open-source packet analyzer. 
Usage 

• Network troubleshooting
  Analysis software
  Communications protocol development

Fiddler captures HTTP and HTTPS traffic data between browsers and servers.

Overview
Fiddler sits between the HTTP client and server and listened on a port.
The requests is sent to Fiddler proxy bridge rather than the real server, Fiddler forward the request to server and receive the response and then back to browser.



Using Fiddler
Download and install Fiddler.

Check overall Web sessions
Open a web page in a browser.
Fiddler lists the web requests in web sessions panel, while if you visit more web pages, the recorded requests will continue growing and keep in order.
Information displayed in web session :

• # Request ID generated by Fiddler
• Result : Result code from the HTTP response
• Protocol : The protocol (HTTP / HTTPS / FTP) used by this session
• Host : Hostname of the server to which the request was sent
• URL : The path and file requested from the server
• Body : The number of bytes in the response body
• Caching : Values from the response’s expires or Cache-Control headers
• Process : The local Windows process from which the traffic originated
• Content-Type : The Content-Type header from the response
• Custom : A text field you can set via scripting
• Comments : A text field you can set from scripting or the session’s context menu

  
Check Inspectors

Click on a HTTP session, then it will display "Inspectors" tab.

Request Inspectors

• Headers : Request headers and status
• TextView : Request body
• WebForms : Request parameters and fields data
• HexView : Request body in a hexadecimal view
• Auth : Authentication parameters
• Cookies : Cookies data in key / value pairs
• XML , JSON : Request body as an XML DOM in a tree view or JSON

Response Inspectors

• Transformer : Removes GZip, DEFLATE, and CHUNKED encodings for easier debugging
• Headers : Response headers and status
• TextView : Response body
• HexView : Response body in a hexadecimal view
• ImageView : Response body as an Image. Supports all .NET image formats.
• XML : Shows the response body as an XML DOM in a tree view
• Privacy : Provides P3P statement in the response headers, if present

 

Check statistics

It show the estimated performance statistics for the selected HTTP sessions.

It is useful for performance turning.