|Revision 1.0||01.15.2013||Admin||Fiddler tutorial|
|Revision 1.1 – 1.3||09.09.2013 – 10.04.2013||Admin||bugfixes and enhancements|
Fiddler is a free and open-source packet analyzer. It is used for network troubleshooting, analysis, software, communications protocol development and education. Fiddler captures HTTP and HTTPS traffic data between browsers and servers. These data are extremely valuable for troubleshooting, performance turning and system monitoring. This article is a step by step tutorial to guide how to use Fiddler and capture HTTP Traffic.
On 12 September 2012 Eric Lawrence announced that Fiddler was acquired by Telerik and he would join the company to work on Fiddler on a full-time basis.
- 1. Fiddler Overview
- 2. Download Fiddler
- 3. Install Fiddler on your client machine
- 4. Start Fiddler
- 5. Use Fiddler to Capture HTTP or HTTPS traffic
- 5.1 Check overall Web sessions
- 5.2 Check Fiddler Inspectors
- 5.3 Check statistics of the request
- 6. This Fiddler tutorial is done, leave a question or comment to us if you have
1. Fiddler Overview
Fiddler sits between HTTP client and server and listened on a port. As the finger below, it acts as €œman-in-the-middle€ proxy, when using fiddler, the requests is being sent directly to Fiddler proxy bridge, Fiddler will forward the request to real server, Likewise, the response from server is also sent to the fiddler, fiddler will forward it to the browser. To the client browser, Fiddler claims to be the web server, and to the web server, Fiddler mimics the web browser. In this process, Fiddler intercepts and records all the incoming and outgoing messages.
Besides Fiddler, FireBug is an alternative one and most popular and powerful web development tool, it can Inspect HTML and modify style and layout in real-time.
2. Download Fiddler
Fiddler is a Windows Forms application, available for Windows XP and later, go to download page http://www.fiddler2.com/fiddler2/, there have two versions fiddler2 and fiddler4 available, fiddler2 was written in .Net 2, fiddler4 was higher, please choose either the one to download.
3. Install Fiddler on your client machine
After downloaded, double-click the exe file and agree with the installation license, follow the step-by-step wizard to complete the installation, during installing, you may be asked to close all browsers.
4. Start Fiddler
Lunch the shortcut of Fiddler from from Start > All Program, you will see the below main Fiddler UI, when starting Fiddler, it will automatically check the latest version against the Fiddler server and ask you upgrade if there have new version available.
5. Use Fiddler to Capture HTTP or HTTPS traffic
5.1 Check overall Web sessions
Use Internet Explorer or Mozilla FireFox, open a web page that sends a request via the explorer, we will instantly see a list of the web requests in the web sessions panel, while, if you visit more web pages, the recorded requests will continue growing and keep in order.
The web sessions show all HTTP and HTTPS sessions captured by Fiddler, the messages include certain key information:
- # – An ID# of the request generated by Fiddler for your convenience
- Result – The Result code from the HTTP Response
- Protocol – The Protocol (HTTP/HTTPS/FTP) used by this session
- Host – The 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
The each type of item have an own icon on the left hand, the below is the list of the all icons.
Of course, It’s just an overall summary list, it give a generic sense that we can choose what we want.
5.2 Check Fiddler Inspectors
If you double click on a HTTP session, the Inspectors tab on right hand will be displayed, it visualize requests or response content in meaningful ways. In the top half of the right hand side is the request what was sent to server, there have multiple tabs of view where show format message and data(Headers, Text View, web forms, HexView, Auth, Cookies, Raw, JSON and XML). The first one is header, it logged cache, Client, Cookies/Login, Miscellaneous and Transport, these infos are particular helpful to troubleshoot.
[RW] Headers Shows request headers and status.
[RW] TextView Shows the request body in a text box.
[RW] HexView Shows the request body in a hexadecimal view.
[RO] XML Shows the request body as an XML DOM in a tree view.
[RW] Transformer Removes GZip, DEFLATE, and CHUNKED encodings for easier debugging.
[RW] Headers Shows response headers and status.
[RW] TextView Shows the response body in a text box.
[RW] HexView Shows the response body in a hexadecimal view.
[RO] ImageView Shows the response body as an Image. Supports all .NET image formats.
[RO] XML Shows the response body as an XML DOM in a tree view.
[RO] Privacy Explains the P3P statement in the response headers, if present.
The bottom half is the response tab, this is the entire response being sent back to the client browser, it may possible be HTML page, image, JSON string, Cascading Style Sheet (CSS) and other resources, we can click textview, syntaxview, Imageview and other clickable tab to view it in different format, the below example demos we syntax view the html source page of this site.
5.3 Check statistics of the request
For instance, the below is the analytic data which retrieved the home page of this site.
Bytes Sent: 1,178 (headers:1,178; body:0)
Bytes Received: 148 (headers:148; body:0)ACTUAL PERFORMANCE
Determine Gateway: 47ms
DNS Lookup: 0ms
TCP/IP Connect: 452ms
HTTPS Handshake: 0ms
ClientDoneResponse: 21:44:56.012Overall Elapsed: 0:00:01.362RESPONSE BYTES (by Content-Type)
ESTIMATED WORLDWIDE PERFORMANCE
The following are VERY rough estimates of download times when hitting servers based in WA, USA.US West Coast (Modem – 6KB/sec)
Elapsed: 0.10sJapan / Northern Europe (Modem)
Elapsed: 0.15sChina (Modem)
Elapsed: 0.45sUS West Coast (DSL – 30KB/sec)
Elapsed: 0.10sJapan / Northern Europe (DSL)
Elapsed: 0.15sChina (DSL)
6. This Fiddler tutorial is done, leave a question or comment to us if you have
In this tutorial introduces the basic features and examples of Fiddler, Fiddler is a very good debug tool. You may take a try if you have not tried it.