Ad blocker interference
Learn how ad blockers affect SDK requests and how to prevent it.
Ad blockers and privacy extensions can interfere with optimization and analytics tools by blocking requests to known third-party domains. This is common across platforms in this space and does not affect only Croct. Understanding how these tools work helps you anticipate the impact and take steps to prevent data loss.
How ad blockers work
Ad blockers rely on community-maintained filter lists, such as EasyList and EasyPrivacy, to decide which requests to block. These lists contain patterns that match known advertising, analytics, and tracking domains.
When your application makes a request, the ad blocker checks the URL against its filter list. If the domain or path matches a known pattern, the browser silently blocks the request before it reaches the server. This filtering happens at the network level, which means your application code receives no response and typically no error.
Because filter lists target domains associated with data collection, any vendor in the analytics or optimization space can be affected, regardless of how they handle user data.
What gets blocked
The SDK communicates with three endpoints, each serving a different purpose:
| Path | Description |
|---|---|
| /client/web/evaluate | Evaluates queries for audience targeting. When blocked, personalization rules and audience conditions cannot be resolved. |
| /client/web/track | Sends events to the analytics pipeline. When blocked, behavioral data is lost, leading to gaps in analytics. |
| /content | Retrieves personalized content from slots. When blocked, the application falls back to default content or shows nothing. |
When an ad blocker targets the API domain, it can block any combination of these endpoints. The effect depends on which requests the filter list matches.
Impact on your application
When ad blockers interfere with SDK requests, you may notice symptoms like:
- Incomplete analytics: Events from visitors using ad blockers never reach the server, creating a blind spot in your data. Metrics like conversion rates and engagement scores undercount actual activity.
- Inconsistent experiences: Visitors with ad blockers may see default or missing content where others see personalized experiences. This creates an uneven user experience that is difficult to detect without monitoring.
- Reduced audience accuracy: When the SDK cannot track behavior or evaluate queries, audience segments based on that data become less reliable. Experiments and targeting rules operate on a partial view of your traffic.
These are not bugs in your application or in the SDK. They are a side effect of how ad blockers filter network traffic. The most effective way to prevent this interference is to route API calls through your own domain so they are not flagged by filter lists.