Google Online Security Blog: Improving Security and Privacy for Extensions Users
This has been a controversial change since the Web Request API is used by many popular extensions, including ad blockers. We are not preventing the development of ad blockers or stopping users from blocking ads. Instead, we want to help developers, including content blockers, write extensions in a way that protects users’ privacy.
You can read more about the Declarative Net Request API and how it compares to the Web Request API here.
We understand that these changes will require developers to update the way in which their extensions operate. However, we think it is the right choice to enable users to limit the sensitive data they share with third-parties while giving them the ability to curate their own browsing experience. We are continuing to iterate on many aspects of the Manifest V3 design, and are working with the developer community to find solutions that both solve the use cases extensions have today and keep our users safe and in control.