Chrome drops support for old ad blockers: the end of Manifest V2

What happened?

Google has announced that Chrome versions 150 and 151, scheduled for late June and July respectively, will remove the last fragments of code that allowed old ad blockers (based on Manifest V2) to keep working. According to The Verge, citing 9to5Google, these changes eliminate the technical loopholes that still allowed some V2 extensions to operate. This means that extensions like uBlock Origin, which were already officially discontinued in 2024, will stop working entirely starting with Chrome 151. The move affects millions of users who still relied on these tools to block ads and trackers.

Context: the transition to Manifest V3

The transition from Manifest V2 to V3 officially began in 2024, when Google gradually phased out support for the older extension system. Manifest V2 allowed ad blockers to access the webRequest API, which offered detailed control over network requests, enabling them to block or modify each request in real time. Instead, Google promoted Manifest V3, which uses the declarativeNetRequest API, much more restrictive: it limits the number of blocking rules (to 30,000 per extension, compared to unlimited in V2) and does not allow complex dynamic rules. Google argues that this improves security and performance, as V3 extensions cannot intercept sensitive data. However, critics like the Electronic Frontier Foundation (EFF) have pointed out that Manifest V3 significantly reduces the effectiveness of ad blockers and user privacy, indirectly benefiting Google's advertising business, which generates over $200 billion annually.

Many users migrated to uBlock Origin Lite (a V3 version) or switched to browsers like Firefox, which still supports Manifest V2. However, some V2 blockers kept working thanks to technical loopholes that Google is now closing. According to 9to5Google, the changes in Chrome 150 and 151 remove internal references to V2, preventing any old extension from running.

Why is this important?

This decision affects millions of users who relied on ad blockers to improve their browsing experience, protect their privacy, and save bandwidth. According to StatCounter data, Chrome has a global market share of over 65%, meaning any change in its ecosystem impacts the majority of internet users. Moreover, it raises questions about Google's control over the web ecosystem, given that its business model heavily depends on advertising. This move is not new: in 2019, Google already limited blocking capabilities in Chrome with changes to the extension API, and in 2020, the company delayed the transition to Manifest V3 after criticism from developers and regulators. However, it now seems determined to complete the change.

The impact on privacy is significant. Ad blockers not only remove ads but also protect against trackers and malware. Without them, users are exposed to tracking networks like those of Google, Facebook, and other actors. Additionally, data consumption and page load speed are affected: a 2023 study by the University of Michigan found that ad blockers reduce web page load time by an average of 20%.

Consequences

• For users: Those who do not migrate to V3 blockers or switch browsers will be exposed to ads and trackers. It is estimated that over 30% of Chrome users use ad blockers (according to PageFair), and many still use V2 versions. The forced migration may cause confusion and loss of functionality, as V3 alternatives are less effective. For example, uBlock Origin Lite can only block up to 30,000 rules, while the original uBlock Origin could handle hundreds of thousands.
• For developers: Less freedom to create advanced blocking extensions; the declarativeNetRequest API imposes limits on the number of rules and their complexity. Developers of extensions like NoScript or uMatrix have also been affected, as their functionalities depended on webRequest. Some have chosen not to migrate to V3, reducing the availability of privacy tools.
• For the market: An increase in migration to browsers like Firefox, Brave, or Edge (which still supports V2) is expected. According to StatCounter data, Firefox has lost market share in recent years (around 3% in 2024), but this measure could slow its decline. Brave, which blocks ads by default, could also benefit. Additionally, alternative browsers like Vivaldi or Opera could gain users. However, Chrome's inertia is enormous: switching browsers means losing extensions, bookmarks, and settings, which many users avoid.

What should readers know?

If you use Chrome and a Manifest V2-based ad blocker (like the original uBlock Origin), you should switch to a V3 alternative (like uBlock Origin Lite, AdBlock Plus, or Ghostery) or migrate to another browser. Firefox still supports Manifest V2 and offers greater customization freedom. You can also consider Brave, which integrates native ad blocking and is based on Chromium, but with more privacy-friendly policies.

Google defends that Manifest V3 improves security and performance, but critics point out that it is an anticompetitive move to protect its advertising business. In fact, the company has already been fined for anticompetitive practices in Europe (such as the €4.34 billion fine in 2018 for abusing its dominant position in Android). Additionally, the U.S. Department of Justice has initiated an antitrust case against Google over its dominance in digital advertising, which could be influenced by this decision. In any case, the transition to Manifest V3 is irreversible in Chrome, so users should take action before July 2026.