On May 18, Mozilla senior software engineer Rob Wu announced in a blog post that the Firefox browser will fully adopt Manifest V3 by the end of 2022. Before that, Firefox will launch a new developer preview program ahead of time to collect feedback from web developers.
Limiting ad blockers, Manifest V3 sparks controversy
Manifest V3 is the next iteration of the web augmentation platform, first released by Google in 2019 to improve user privacy, security and performance. However, Manifest V3 caused a lot of controversy after its release. Some people criticized it for significantly limiting functions such as ad blockers. The Electronic Frontier Foundation (EFF) directly stated that “Manifest V3 is deceptive and threatening.”
The most controversial change in Manifest V3 is the replacement of the WebRequest API with the Declarative Net Request API, allowing pattern matching rules to be set to detect the requested traffic and take action, but Google imposes a cap on the number of rules, and one of the most common uses of the WebRequest API is Blocks ads, so this move will severely impact the usability of ads and content mask extensions.
Google explained that Chrome extensions have permission to read and modify page content, which provides many conveniences but also brings privacy and security risks when users install malicious or compromised extensions, and some extensions may abuse WebRequest, further increase security risks.
But there are also many people who suspect that Google’s move is to protect its own news feed ads. After all, Google has emphasized in its financial reports that ad-blocking technology is a threat that “may adversely affect our operating results.”
The current situation is that Google Chrome has stopped accepting new extensions based on Manifest V2. The following are two key time points:
- January 17, 2022: The Chrome Web Store will no longer accept new Manifest V2 extensions, developers can still push updates to existing Manifest V2 extensions, but cannot submit new Manifest V2 extensions.
- January 2023: Chrome will no longer support running Manifest V2 extensions, and developers will not be able to push updates to existing Manifest V2 extensions.
Firefox will take a different approach than Chrome
Mozilla also mentioned the controversy in a blog post, for which Mozilla said it would take a different approach than Google Chrome when implementing Manifest V3. Mozilla proposes that the Declarative Net Request API is not exactly a perfect replacement for the WebRequest API, limiting the scope of ad maskers and privacy extensions.
“Mozilla will retain support for ‘blocking WebRequest’ in Manifest V3. For maximum compatibility with other browsers, the Declarative Net Request API will also be supported,” Mozilla said in a blog post. “Content blocking is one of the most important features of an extension, and we’re committed to ensuring that Firefox users have access to the best privacy tools.”
At the same time, Mozilla also mentioned in the article that they found that the Service Worker used by Chrome did not fully support the various use cases it considered important, and required developers to rewrite a large part of the extension code. To this end, Mozilla proposed Event Pages to solve these problems, and said that Event Pages were welcomed by the community. Mozilla says it will also support Service Workers for compatibility reasons, as Mozilla recognizes them as an event-driven environment with a defined lifespan, already part of the web platform and with good cross-browser support.
“In Firefox, we have decided to support event tabs in Manifest V3, and our developer preview will not include Service Workers (an ongoing effort to support these service workers for future versions). This will make it easier for developers to Migrate existing persistent background pages to support Manifest V3 while retaining access to all DOM-related functionality in Manifest V2.”
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