Study Finds Chrome's Manifest v3 Update Doesn't Weaken Ad Blockers, Upholding User Privacy

A comprehensive study from Goethe University Frankfurt has delivered surprising findings about Google Chrome's Manifest v3 (MV3) extension architecture, revealing that ad-blocking and anti-tracking capabilities remain robust despite widespread concerns that the update would weaken privacy protections. Published in the peer-reviewed Proceedings on Privacy Enhancing Technologies (PoPETs), the research directly challenges predictions that MV3 would cripple tools users rely on to exercise their privacy rights under regulations like GDPR and CCPA.

Researchers Karlo Lukic and Lazaros Papadopoulos conducted rigorous testing comparing MV3 with the previous Manifest v2 (MV2) framework using default filter settings from popular ad-blocking extensions. Their analysis demonstrated "no statistically significant reduction in ad-blocking or anti-tracking effectiveness" in MV3 implementations. Surprisingly, MV3 extensions actually blocked 1.8 more tracking scripts per website on average than their MV2 counterparts.

This outcome is particularly significant given Google's introduction of MV3 in 2019, which replaced MV2's powerful chrome.webRequest API with the more restricted chrome.declarativeNetRequest system. The change eliminated synchronous blocking capabilities that could intercept network requests in real-time, prompting warnings from developers that privacy tools would become less effective. Digital rights advocates had expressed concern that weakened ad-blocking would undermine user agency under privacy regulations, as effective tracking prevention is fundamental to GDPR's consent requirements and CCPA's opt-out provisions.

The study's findings suggest users can maintain confidence in ad-blocking extensions as privacy safeguards. As Papadopoulos noted: "There could be minor cosmetic reasons to prefer MV2, but nothing that significantly impacts privacy negatively." This potentially reduces pressure on users to switch browsers solely for MV2 compatibility, though researchers caution this represents a "snapshot in time" and future MV3 changes could alter the landscape.

Important limitations remain: The study didn't evaluate performance impacts like page load speeds, nor did it test whether MV3's 330,000-rule limit might affect less-visited websites. Extension developers also continue raising concerns about Chrome Web Store oversight and delayed feature improvements.

For privacy-conscious users and organizations managing compliance programs, these findings offer reassurance that Chrome extensions remain viable tools for enforcing privacy preferences. However, ongoing vigilance is required as Google continues evolving its extension framework while balancing competing interests between user privacy, security, and its advertising ecosystem.