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Auto blocking in detail

Updated

Important

  • The Auto-blocking is not available for customers using Enterprise, Premium, or Advanced packages.
  • This feature is supported for Corporate customers with the following packages: Essential, Plus, Pro, and Business
  • If your Admin Interface does not display the Auto-blocking implementation option, your account does not support this feature.

Enabling Auto Blocking

To enable the Auto Blocking feature an additional script needs to be loaded along with the main loader.js script:

<script src="https://web.cmp.usercentrics.eu/modules/autoblocker.js"></script>
<script
 id="usercentrics-cmp"
 src="https://web.cmp.usercentrics.eu/ui/loader.js"
 data-settings-id="y05NPaJsbGnT2v"
 async
></script>
Screenshot 2026-03-16 at 13.44.14.png

Understanding Auto Blocking

Identifying services

Auto blocking relies on information collected by the scanner. The scanner essentially detects third-party server calls and logs these as data processing services. 

Services that have been added to the Admin that match the findings of the scanner are compiled into a list of instructions which essentially lists the services by service ID and then a method to recognize the element. These are in order of priority:

  1. Tag id
  2. Tag src
  3. hash (Essentially a resource is encoded and compared to the previously encoded resource.)

The file will look similar to this:

{
  "nodes": [
    {
      "serviceIds": [
        "H1Vl5NidjWX"
      ],
      "hash": "4013037056144",
      "src": "https://web.cmp.usercentrics-sandbox.eu/ui/loader.js",
      "id": "usercentrics-cmp"
    },
    {
      "serviceIds": [
        "H1Vl5NidjWX"
      ],
      "hash": "3809307713796",
      "src": "https://web.cmp.usercentrics-sandbox.eu/modules/autoblocker.js"
    },
    {
      "serviceIds": [
        "BJz7qNsdj-7",
        "H1PKqNodoWQ",
        "rw4DyFQcg6s3-W"
      ],
      "hash": "13409490399530",
      "src": "https://www.youtube-nocookie.com/embed/bp612TdEK1c"
    },
    {
      "serviceIds": [
        "BJz7qNsdj-7",
        "9V8bg4D63",
        "S1_9Vsuj-Q"
      ],
      "hash": "16595230151636",
      "src": "https://www.youtube.com/embed/tROVq1lW0IU?si=VMdGX-0tbe-6Ed7d"
    }
  ]
}

Please note

  • Multiple resources can share the same service ID. All these resources are (un)blocked when the corresponding service is (dis)allowed.
  • A single resource can also have multiple service IDs. For this resource to be allowed to load, all these services must be consented to.
  • Unknown services, or services that aren't added to the CMP are not added to this checkfile.

Blocking services prior consent

When an element on the website matches an entry in the checkfile it is added to the DOM pre-marked up; i.e.:

  • Scripts have their type set to "text/plain" to load it, but prevent it from executing.
  • Iframes and images have their src replaced with data-uc-src to prevent the resource from being fetched and loaded.

For all elements the data-uc-hash attribute is added to allow the CMP to identify which elements belong to what service, and thus whether it is allowed to load.

Overriding the Auto Blocking feature

It's possible to prevent the Auto Blocking feature from blocking a resource by manually adding the data-uc-allowed="true" attribute. This ensures that the Auto Blocking feature won't block the resource.

You can combine the use of the Auto Blocking feature and manual mark up.

The Auto Blocking feature respects mark up and checks to see if the element is already marked up (the script has type="text/plain" or the generic element doesn't have a src), if this is the case the element is disregared.

Important

The auto-blocking feature works most effectively when third-party service scripts are implemented directly in the website’s source code. In this setup, the Usercentrics CMP can detect and block scripts before they are executed until user consent is provided.

If third-party services are implemented through Google Tag Manager (GTM), the auto-blocking mechanism may not function reliably. This is because GTM loads and executes tags asynchronously after the page has started loading.

For websites using Google Tag Manager, it is recommended to manage consent and trigger tags through Google Tag Manager consent configurations or tag triggers, rather than relying on the auto-blocking mechanism.

 

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