Configuring a Private Instance of WebPagetest with browser extensions

Karan Kumar


Configuring a private instance of WebPagetest allows you to make modifications to test browser extensions such ad blockers. Out of the box, most of these extensions will not work well with WebPagetest. On an empty browser cache, they typically open a new tab and ask users to make configuration changes or ask for a donation. Updated copies of the extensions are available for download. Alternatively, instructions on how to configure on your own are provided below.

For our ad blocker study we used the following steps:


  • Remote desktop software
  • WebPagetest private instance
  • Administrator access to private WebPagetest instance
  • Modified AdBlock Plus extension


  1. Configure a private WebPagetest instance using these steps.
  2. Remote desktop to the wpt agent instance where you want to set up these browsers along with extensions.
  3. Install the AdBlock Plus extension:
    1. Access Adblock Plus from chrome web store
    2. Go to chrome://extensions/ and note the extension ID of Adblock Plus. For example, signature extension_id = cfhdojbkjhnklbpkdaibdccddilifddb
      Adblock Plus
    3. Go to chrome://version/ and copy the Profile Path.
    4. Open a terminal and cd into $Profile
    5. Open adblockplus.js in a text editor
    6. Modify the following line to suppress ad blockers from opening their default page. This enables AdBlock Plus to work well with WebPagetest.
      defaults.suppress_first_run = true
  4. From the downloaded extension:
    1. Save file on agent’s Desktop.
    2. Unzip this file onto Desktop
    3. Note the path where these folders were created. This will be needed in step 6 example:- C:\Users\Administrator\Desktop\extension\adblockplus
  5. Open the WebPagetest driver settings. The configuration file for this driver is located at C:/WebPagetest/wptdriver.ini
  6. Add the following settings to WebPagetest driver settings file to load adblocking extensions, where the load-extension value is the path notated in step 3c:
    exe="C:\Program Files (x86)\Google\Chrome\Application\chrome.exe" 
    options='--load-extension="%WPTDIR%\extension,C:\Users\Administrator\Desktop\extension\adblockplus" --user-data-dir="%PROFILE%" --no-proxy-server --no-default-browser-check'
  7. SSH into your WebPagetest server and add the following lines to the server settings file, usually located at
    ; ************************************
    ; ****** 2 - ad-us-west-1           *****
    ; ****** AD US West (N. California) *****
    label="AD US West (N. California)"
    label="AD US West (N. California)"
    browser=IE 11
    label="AD US West (N. California)"
  8. Restart WebPagetest server. You should see the following in your WebPagetest portal:

With these steps you can test the impact ad blockers or other browser extensions have on the performance of your applications.

Learn more about Instart Logic:

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