Merge pull request #675 from AdguardTeam/agm-2388-kb-urltransform-modifier-example

[AGM-2388] Updated the article in KB about the urltransform modifier example

Author: DashaBu

docs/general/ad-filtering/create-own-filters.md

@@ -2951,6 +2951,32 @@ the request to `https://example.com/firstpath` will be blocked.
 
 `$urltransform` rules can also be disabled by `$document` and `$urlblock` exception rules. But basic exception rules without modifiers do not do that. For example, `@@||example.com^` will not disable `$urltransform=/X/Y/` for requests to **example.com**, but `@@||example.com^$urlblock` will.
 
+**The rule example for cleaning affiliate links**
+
+Many websites use tracking URLs to monitor clicks before redirecting to the actual destination. These URLs contain marketing parameters and analytics tokens that can be removed to improve privacy.
+
+Below is an example of how to obtain the clean destination link to bypass tracking websites and go directly to the destination.
+
+In our example:
+
+ 1. The initial URL (with click tracking): `https://www.aff.example.com/visit?url=https%3A%2F%2Fwww.somestore.com%2F%26referrer%3Dhttps%3A%2F%2Fwww.aff.example.com%2F%26ref%3Dref-123`
+ 1. Tracking URL after decoding special characters: `https://www.aff.example.com/visit?url=https://www.somestore.com/`
+ 1. The website you want to visit: `https://www.somestore.com`
+
+To clean the URL, we first need to decode special characters (like `%3A` → `:`, `%2F` → `/`, etc.) and extract the real URL from the tracking parameters. We will use the `$urltransform` modifier to do this. The following 4 rules replace URL-encoded symbols with their real characters:
+
+`/^https?:\/\/(?:[a-z0-9-]+\.)*?aff\.example\.com\/visit\?url=/$urltransform=/%3A/:/`
+`/^https?:\/\/(?:[a-z0-9-]+\.)*?aff\.example\.com\/visit\?url=/$urltransform=/%2F/\//`
+`/^https?:\/\/(?:[a-z0-9-]+\.)*?aff\.example\.com\/visit\?url=/$urltransform=/%3F/?/`
+`/^https?:\/\/(?:[a-z0-9-]+\.)*?aff\.example\.com\/visit\?url=/$urltransform=/%3D/=/`
+`/^https?:\/\/(?:[a-z0-9-]+\.)*?aff\.example\.com\/visit\?url=/$urltransform=/%26/&/`
+
+After that, we need to write the rule that will block the tracking website and redirect you directly to the target address (somestore.com):
+
+`/^https?:\/\/(?:[a-z0-9-]+\.)*?aff\.example\.com\/visit\?url=/$urltransform=/^https?:\/\/(?:[a-z0-9-]+\.)*?aff\.example\.com.*url=([^&]*).*/\$1/`
+
+Tracking links will now be automatically cleaned up, allowing direct navigation to the destination website without tracking.
+
 :::caution Restrictions
 
 Rules with the `$urltransform` modifier can only be used [**in trusted filters**](#trusted-filters).