Apple’s Move to Block User Tracking Spawns New Digital Ad Strategies

As Apple Inc. moves ahead with long-promised plans to make it harder to target certain iPhone users with ads, advertising companies and software developers are preparing for major disruptions to the $400 billion digital advertising industry.

Facebook Inc., gaming companies and ad-tech providers are weighing a variety of responses, including updated payment models, new advertising techniques and notifications for users. In China, social-media apps have tested a potential workaround that would continue tracking users’ digital footprints.

The changes to Apple’s iPhone software — part of what the company describes as an app-tracking transparency initiative meant to protect user privacy — will let users decide whether to allow apps to track them for targeted ads.

The iPhone maker first announced the plan in June and intended to roll it out in September, before…