> For the complete documentation index, see [llms.txt](https://server-side.docs.sirdata.net/sirdata-server-side/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://server-side.docs.sirdata.net/sirdata-server-side/english-1/f.a.q-server-side/ad-blocking/ad-blocker-operation.md).

# Ad-Blocker Operation

An ad-blocker analyzes all requests sent by the web browser and compares them to specific criteria to decide whether they should be blocked. When a request matches these criteria, it is intercepted and blocked before reaching its destination.

**Request Evaluation Process**

1. **Request Inspection**: Each HTTP/HTTPS request sent by the browser is examined in real-time.
2. **Comparison to Block Lists**: The ad-blocker refers to block lists maintained by communities or specialized organizations. These lists, constantly updated, contain rules to identify requests related to tracking and advertising.

**Block Lists**

Block lists are files that define the criteria for recognizing malicious or undesirable requests. For example, the **EasyPrivacy** list is often used to block requests related to user tracking. Here’s a link to this list: **EasyPrivacy**.

**Examples of strings in these lists**:

* `.js?id=GTM-`
* `googletagmanager.com`
* `/gtag/js?`

These strings primarily target tracking services such as Google Tag Manager and Google Analytics. If no action is taken to avoid blocking, these services will be systematically blocked by ad-blockers.

**Updates and Bypasses**

Block lists are regularly updated to adapt to new bypass techniques deployed by advertisers or tracking platforms. As a result, innovation in bypassing ad-blockers is a constant challenge. Each new version of the lists requires monitoring and adjustments to restore tracking or advertising functionality.


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