How to test an ad blocker and understand the results

Create a clean test condition

Update the browser and blocker, close duplicate test tabs, and verify that the extension is enabled for the test site. If you use strict browser protection, DNS filtering, a VPN, or multiple blockers, note that first; any of them can change the result.

Run the test once in a normal window. Then repeat in a fresh private window only if the blocker is allowed there. Do not compare the two results unless the extension permissions are the same.

Read categories separately

Failure in one group does not mean nothing is blocked. It may mean the filter list does not cover that endpoint, the browser limits the extension API, or another setting changed the path used by the test.

• A request test checks whether a known resource can load over the network.
• A pixel test uses a tiny image or beacon commonly associated with measurement.
• An analytics test checks endpoints used for audience or behavior reporting.
• A cosmetic test checks whether a visible placeholder is hidden after page layout.

Troubleshoot in a useful order

• Reload the test page once with the browser cache bypassed.
• Confirm the current site is not paused or allow-listed.
• Update the extension’s filter lists if it offers that control.
• Disable other privacy extensions temporarily to remove overlap.
• Repeat in a separate browser profile before changing system-wide DNS or network settings.

Record what changed

Write down the browser version, blocker version, enabled lists, and test time when comparing two configurations. A screenshot is helpful, but the settings explain the result. If you report a problem, include the failed category and whether the resource was visible, loaded in developer tools, or both.