First Steps with Fiddler Everywhere on Linux

This tutorial describes how to install and start using Fiddler Everywhere on Linux.

  • First, you will go through the installation and configuration steps.
  • Next, you'll create a Fiddler account so that you can move on to using the web-debugging tool.
  • Finally, you will see how to capture, inspect, and modify traffic.


  • Install Ubuntu 20+ x64.

  • Provide 400MB of free disk space.

  • Create an account with administrative rights, which you'll need for capturing and decoding HTTPS traffic.

  • Provide an active Internet connection with access to the following URLs:


    The Telerik site (where the Fiddler authentication form resides) uses different CDNs to load various components, styles, and cookies related to its user interface. Having limited internet access can cause the site not to load correctly.

  • Ensure that Fiddler Everywhere's proxy port is open and unrestricted by a firewall/security tool. By default, that's port 8866, but you can change it from Settings > Connections > Fiddler listens on port.

Step 1: Install Fiddler Everywhere on Your Machine

Install the latest version of Fiddler Everywhere on your machine.

  1. Download the latest version of Fiddler Everywhere.

  2. Install the downloaded package. On most Linux distributions, you must set the installation file as executable before starting the installation. To achieve this, either use the command line or the GUI of the desired distribution:

    • Setting the installation plan as executable through the command line:

      1. Open a terminal.

      2. Navigate to the folder where the installation file resides.

      3. Type sudo chmod +x filename.appimage. You can omit the sudo command if the currently logged user is the one that downloaded the executable.

      4. If prompted, enter your username and password. Press the Enter key.

    • Setting the installation plan as executable through the GUI.

      For the Gnome distribution

      Gnome setting executable

      For the Cinnamon distribution

      Cinnamon setting executable

      For the KDI distribution

      KDE setting executable

Step 2: Create Your Fiddler Account

In this step, you'll register by creating your unified Telerik account.

  1. Launch the Fiddler Everywhere application. Follow the Sign in or create an account link.

  2. Create an account using email and password or using the Sign in with Google option.

    The Fiddler Everywhere Enterprise subscription plan supports SSO login. Get in touch with our support for detailed instructions on configuring your company-specific SSO.

  3. Enter the requested information on the Enter Your Email to Sign in or Create an Account screen.

  4. Check your inbox, open the confirmation email, and complete your account activation.

  5. Return the Fiddler Everywhere application and choose whether to become a trial user or purchase a subscription plan by selecting either the Start Free Trial or the BUY NOW link.

After successful login into Fiddler Everywhere, you will see your personal and license information within the Home pane.

Step 3: Interact with the Captured Traffic

You can now take advantage of the Fiddler Everywhere capabilities - capture, inspect, save & share, import *& export, mock and modify HTTPS traffic.

  1. Capture HTTPS traffic through the preferred capturing mode.

    To capture and decrypt secure HTTPS traffic, you will need to explicitly install and trust the Fiddler certificate authority (CA). Alternatively, you can explicitly install the Fiddler CA in a third-party certificate store (for example, through intalling the CA in Firefox) and capture traffic only from that application.

  2. Inspect the captured data.

  3. Save, share. or export the captured HTTPS traffic.

  4. Modify a session through the Composer

  5. Mock client and server behavior through the Rules tab

The Rules tab is one of the most advanced features in Fiddler Everywhere. You can create and execute complex rules on your incoming traffic to mock client and server behavior without touching the client and server applications.

That's it! Now you're equipped to delve deeper into Fiddler Everywhere and make the most of its powerful functionalities.

Next Steps