Firefox Extensions Must Disclose Data Collection Starting November 2025

Introduction

Mozilla is implementing significant privacy enhancements for Firefox users, requiring all new browser extensions to clearly disclose their data collection practices starting November 2025. This move strengthens user transparency in the evolving landscape of web browser security.

New Data Collection Disclosure Requirements

Beginning November 3, 2025, all newly submitted Firefox extensions must specify within their manifest.json file whether they collect or transmit personal user data. Developers will utilize the browser_specific_settings.gecko.data_collection_permissions key to declare their data handling practices. Even extensions that don't collect any personal information must explicitly state this using the "none" value within the manifest property.

This requirement initially applies only to newly created extensions, with existing published extensions exempt from compliance until they submit updated versions. The transparency initiative represents a major step forward for privacy checker capabilities within browser ecosystems.

User Visibility and Implementation Details

Firefox will display extension data collection information during the installation process alongside traditional permission requests. Users can also review this data on the extension's AMO listing page and within the Permissions and Data section of Firefox's about:addons management interface.

For extensions supporting older Firefox versions (desktop versions before 140, Android before 142), developers must maintain alternative methods for informing users about data practices immediately after installation. This ensures compatibility across different secure browser versions while maintaining privacy standards.

Pros and Cons

Advantages

• Enhanced user privacy awareness and control
• Standardized data collection reporting across extensions
• Clear visibility during extension installation process
• Improved trust in Firefox extension ecosystem
• Better alignment with modern privacy regulations
• Reduced hidden data harvesting risks
• Streamlined compliance for extension developers

Disadvantages

• Additional development overhead for creators
• Potential confusion during transition period
• Limited impact on existing extensions initially
• Possible rejection for non-compliant submissions

Conclusion

Mozilla's new data collection disclosure mandate represents a significant advancement for browser extension manager transparency and user privacy protection. By requiring explicit declarations of data practices, Firefox continues its commitment to putting users in control of their personal information. The November 2025 implementation gives developers ample time to adapt while ensuring future extensions meet elevated privacy standards that benefit the entire browsing community.