Starting with iOS 17, iPadOS 17, and macOS Sonoma, Safari automatically removes tracking parameters from URLs while in Private Browsing Mode, in order to prevent cross-website tracking. When a tracking parameter is detected while browsing or copying a link, Apple says Safari strips the identifying components of the URL, while leaving the rest intact. The links will still work as expected, but will no longer have unique identifiers.
Apple calls this new feature Advanced Tracking and Fingerprinting Protection, and it also works for links shared in the Messages and Mail apps. It can even be enabled for regular Safari browsing. On the iPhone, open the Settings app, tap Safari → Advanced → Advanced Tracking and Fingerprinting Protection, and select All Browsing. Users can also turn off the feature in this menu if they prefer not to use it at all.
In a WWDC 2023 video for developers, Apple shared an example of a URL before and after the tracking parameters are removed. The original URL has a unique "click_id" parameter that advertisers can use to track a user's activity across websites. Safari automatically removes this parameter to protect the user's privacy.
iOS 17 and macOS Sonoma will be released later this year, and are currently available in beta for users with an Apple developer account.