Firefox: New Extensions Must Disclose Data Collection
In November, new Firefox extensions must specify in their manifest which user data they collect. This will soon apply to existing extensions as well.
(Image: David Esser/Shutterstock.com)
Starting November 3, 2025, developers of new Firefox extensions will be required to declare in their manifest file what personal user data their software collects or transmits. This information must be stored in the browser_specific_settings.gecko.data_collection_permissions key of the manifest.json file.
Initially, the regulation will apply exclusively to newly submitted extensions. Updates to existing add-ons are exempt from this obligation for now. Furthermore, extensions that do not collect data must explicitly declare this by entering “none required.” Once an extension uses the new keys for the first time, they will be mandatory for all future versions.
In the future, Firefox will display the information declared by the developer directly in the installation dialog, along with the requested permissions. Additionally, the information will be visible on the detail page of the respective extension on addons.mozilla.org and in the “Permissions and Data” section of the about:addons page in Firefox. With this, Mozilla is implementing the standardization of data collection dialogs announced in April.
For extensions that still support older Firefox versions prior to 140 (Desktop) or 142 (Android), transitional regulations apply: In this case, developers must continue to offer users their option to control data collection immediately after installation.
Consequences for Missing Information
Extensions that do not correctly set the required declarations will no longer be allowed for signing on addons.mozilla.org in the future. The system will notify developers of the problem with an error message. Mozilla aims to ensure that users are transparently informed about how their data is handled before installation.
The documentation published in the Extension Workshop shows developers which specific data types they need to declare. These include, among others, browser history, location data, or personal communication.
Videos by heise
Expansion to All Extensions Planned
In the first half of 2026, Mozilla plans to extend the requirements to all Firefox extensions, including existing add-ons. The company will announce details about this transition and additional tools for developers and users in due course via the Add-ons Blog. The phased introduction is intended to give developers time to adapt their extensions accordingly. All information can be found in Mozilla's blog post.
(fo)
