Capture Web Traffic: Telerik Fiddler First Time Use

When you are browsing the web, you can see words, images, and videos appear on the screen. But do you know what happens behind the scenes? Every time you load a web page, watch a video, click a button, or Like a friend’s post you are generating web traffic. Web traffic is data that is being sent to and from your browser. You can see the web traffic by using special tools that act as a proxy and capture all the traffic. We will be learning how to set up our favorite web traffic proxy, Fiddler.

Install Fiddler

The first thing you need to do is to download Fiddler. https://www.telerik.com/download/fiddler
Pop open the installer. Select the defaults. You should now have Fiddler installed.

Inspectors

You are most likely going to spend the majority of your time in the “Inspectors” tab. The Inspectors is a set of tabs that allow you to see the web traffic. There are a lot of options here but the ones that you will probably use are the “Raw” and “JSON” tabs.

The Raw inspector displays the “raw” request and response data including the headers and body.

The JSON inspector formats that body contents, assuming that it is in JSON, into easily readable JSON format.

Enable Decryption

Out of the box Fiddler doesn’t decrypt web traffic. Which HTTPS decryption disabled, the responses are not going to contain any useful or human-readable information. We need to decrypt the data so that we can read it.

1. Open Fiddler if it isn’t already, click the “Tools” option in the menu bar. Then select “Options”.
2. Select the “HTTPS” tab.
3. Check the boxes “Decrypt HTTPS traffic” and “Ignore server certificate errors”.
4. Hit OK
5. You will most likely need to close Fiddler and re-open it.

Now you can open a website and check the traffic in Fiddler on the Inspectors > Raw tab.

What’s next?

Learn more about APIs, Postman, and Fiddler in my course.

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