Mozilla’s Approach to Manifest V: A Game-Changer for Extension Users

In the world of modern browsing, extensions are indispensable tools that allow users to personalize and enhance their online experiences. They range from privacy-focused tools to productivity boosters, helping people navigate the internet in ways that best suit their needs. Almost half of Firefox users have installed at least one extension, and the Firefox ecosystem has become a favorite destination for users seeking to extend their browser functionality.

To make all this possible, developers rely on a platform known as WebExtensions, which provides APIs that allow extensions to interact with web pages and browser features. With the arrival of Manifest V3, the latest iteration of this platform, all major browsers—including Firefox, Chrome, and Safari—are making strides to implement it. However, each browser has a different approach, with significant consequences for the extensions users can install.

Firefox’s Approach to Manifest V3: A Commitment to Choice and Flexibility

Mozilla’s approach to Manifest V3 is rooted in its fundamental mission to prioritize user choice and control. According to Principle 5 of the Mozilla Manifesto, individuals should have the freedom to shape their online experiences. This philosophy drives Firefox’s unique implementation of Manifest V3, which stands in contrast to how other browsers are handling the change.

Here are the main elements of

New APIs for Greater Flexibility: Mozilla is expanding the range of APIs available to developers. Notably, new AI functionalities will allow extensions to perform offline machine learning tasks directly in the browser. This flexibility enables developers to build more powerful and creative extensions that can better meet users’ diverse needs.
Support for Both Manifest V2 and V3: While other browsers like Google Chrome are pushing forward with only Manifest V3 and deprecating Manifest V2, Firefox is embracing both versions. This dual support gives developers more options, leading to greater innovation and ensuring users can still access older but essential extensions.

The Mozilla approach is all about maximizing choice. By keeping both Manifest V2 and V3 support, Firefox users can retain access to powerful extensions like uBlock Origin, a popular ad blocker, even as the browser landscape evolves.

No Limits on Extensions with Firefox: The Power of Choice

Google’s shift to Manifest V3 has already caused friction among users. As of mid-2025, Google plans to end support for extensions built on Manifest V2. One notable casualty of this transition is uBlock Origin, which relies on a Manifest V2 feature called blockingWebRequest. This feature allows the extension to block unwanted content effectively.

Google plans to replace blockingWebRequest with a new feature called declarativeNetRequest, but this change comes with significant limitations. It severely restricts how extensions can filter content, narrowing the scope of what developers can do. For users who rely on comprehensive ad-blocking and privacy tools, this shift is a significant blow.

In contrast, Firefox is taking a more flexible approach. By continuing to support both blockingWebRequest and declarativeNetRequest, Mozilla ensures that developers have the freedom to create more powerful privacy tools. Users benefit from these choices, keeping privacy and customization at the forefront of their experience.

What Undercode Says: Analyzing Firefox’s Strategy

Mozilla’s decision to support both Manifest V2 and V3 while expanding the range of APIs for developers is a crucial move for users and the broader browser extension ecosystem. One of the key distinctions between Mozilla and other browsers is its unwavering commitment to giving users more control over their digital lives. This includes the freedom to choose between different versions of the extension platform and access a broader variety of features.

Support for both Manifest V2 and V3 allows Firefox to maintain compatibility with popular extensions that depend on older APIs, while also embracing the new capabilities of Manifest V3. For users, this means they aren’t forced to abandon extensions they rely on, like ad-blockers and privacy tools. For developers, this flexibility encourages innovation, as they can take full advantage of the latest APIs without being forced into a complete overhaul of their existing extensions.

Moreover, Firefox’s embrace of new AI functionalities for extensions opens up exciting possibilities for developers. Machine learning tasks that were once reliant on cloud computing can now be handled offline directly within the browser. This not only improves privacy by keeping data on the user’s device but also makes browsing faster and more responsive.

Ultimately,

Fact-Checker Results

Manifest V2 Support: Firefox’s dual support for Manifest V2 and V3 is unique and advantageous for users relying on older extension features.
AI Functionalities: New AI capabilities in Firefox extensions may revolutionize offline browsing tools and enhance privacy.
Privacy Focus: Firefox’s approach keeps privacy tools, like uBlock Origin, available to users despite shifts in the broader browser landscape.