Mozilla is implementing a significant transparency requirement for Firefox extensions, mandating that all new browser add-ons disclose their data collection practices to users before installation.
Starting November 3rd, 2025, developers submitting fresh extensions to the Firefox ecosystem must declare whether their software collects or transmits personal data through a new standardized framework embedded in the extension’s core configuration files.
The new data transparency initiative requires extension developers to specify data collection permissions directly within the manifest.json file using the browser_specific_settings.gecko.data_collection_permissions key.
This standardized approach provides Mozilla with consistent metadata about extension behavior across its entire add-on ecosystem.
Extensions that do not collect or transmit any user data must explicitly declare this fact by setting the appropriate “none required” data collection permission in the property, ensuring that privacy-respecting tools receive proper recognition.
Data Collection Policies for Extensions
Developers should note that this requirement applies exclusively to new extensions submitted after November 3rd.
Updated versions of existing extensions are not subject to the mandate during the initial rollout phase, allowing the developer community time to integrate the new framework into their existing projects.
However, once any extension begins utilizing these data_collection_permissions keys in a new version, it must continue implementing them for all subsequent releases.
Extensions failing to comply with requirements when necessary will be blocked from submission to addons.mozilla.org for signing, with clear explanatory messages guiding developers toward compliance.
The disclosed data collection information will be displayed prominently across multiple Mozilla platforms, providing users with comprehensive visibility into extension behavior.
When installing an extension, users will see the data collection details displayed alongside traditional permission prompts, creating a unified authorization experience.
This information will also appear on the addons.mozilla.org extension listing page and within the Permissions and Data section of Firefox’s about:addons management interface.
To maintain compatibility with older Firefox versions, developers supporting Firefox versions prior to 140 on Desktop or 142 on Android must provide users with alternative in-extension controls for managing data collection and transmission immediately after installation.
This backward compatibility consideration ensures that the transition does not alienate users running legacy Firefox versions.
Mozilla is adopting a gradual implementation strategy, beginning with new extensions in November 2025, while planning to extend the requirement to all existing extensions in the first half of 2026.
The company has committed to providing substantial advance notice through the add-ons blog before mandating compliance for legacy extensions, giving developers adequate preparation time.
Furthermore, Mozilla is developing new features to facilitate this transition for both extension developers and end users, though details remain forthcoming.
The initiative represents Mozilla’s broader commitment to browser transparency and user privacy, positioning Firefox as a leader in requiring verifiable disclosure of data practices before users grant extensions system access.
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