The problem is that Google removed a very important API that is crucial for ad blockers. They did that change along with the update to Manifest V3. Mozilla is trying to do the right thing by implementing Manifest V3 without the problem introduced by Google. It will "save" ad-blockers by not removing a specific API that is important for them.
Firefox will keep supporting both V2 and V3. They want to implement V3 in order to avoid forcing most developers to have different manifests for different browsers. This is a good thing in general.
If you want details on what Mozilla is doing, here's a snippet from the linked blog post:
> While other browser vendors introduced declarativeNetRequest (DNR) in favor of blocking Web Request in MV3, Firefox MV3 continues to support blocking Web Request and will support a compatible version of DNR in the future. We believe blocking Web Request is more flexible than DNR, thus allowing for more creative use cases in content blockers and other privacy and security extensions. However, DNR also has important performance and compatibility characteristics we want to support.
Firefox will keep supporting both V2 and V3. They want to implement V3 in order to avoid forcing most developers to have different manifests for different browsers. This is a good thing in general.
If you want details on what Mozilla is doing, here's a snippet from the linked blog post:
> While other browser vendors introduced declarativeNetRequest (DNR) in favor of blocking Web Request in MV3, Firefox MV3 continues to support blocking Web Request and will support a compatible version of DNR in the future. We believe blocking Web Request is more flexible than DNR, thus allowing for more creative use cases in content blockers and other privacy and security extensions. However, DNR also has important performance and compatibility characteristics we want to support.
https://blog.mozilla.org/addons/2022/11/17/manifest-v3-signi...