Mozilla has announced that it will introduce new rules for Firefox extension developers starting November 3, 2025. From that date onwards, all new extensions submitted via addons.mozilla.org must explicitly state whether they collect or transmit personal data.
This information must be included in the extension’s manifest.json file via the new key browser_specific_settings.gecko.data_collection_permissions.
According to Linuxiac, the measure is part of a broader privacy framework with which Mozilla aims to increase transparency towards users. Extensions that do not collect personal data must also explicitly state this by using the value none for this property.
When installing an extension, Firefox will now clearly show what data the extension collects, or whether no data is collected. This information appears next to the standard list of required permissions in the installation window. Mozilla displays the same information on the add-ons website, if the extension is publicly available there, and in the Permissions and Data section on the about:addons page in Firefox.
The new requirement only applies to completely new extensions, not to updates of existing add-ons. However, developers who use the new key once must continue to include it in all subsequent versions. Extensions that do not fill in the field correctly cannot be submitted or signed until the error is corrected.
For developers who support older versions of Firefox, it remains mandatory to provide users with a way to manage data collection immediately after installation. This applies to versions below 140 on desktop and 142 on Android.
First phase of new framework
Mozilla sees this change as the first phase of a broader rollout of the new framework. In the first half of 2026, all extensions, new and existing, will have to comply with these rules. The organization has indicated that it will inform developers in a timely manner and is working on tools to ensure a smooth transition.
With this step, Mozilla aims to give users more insight and control over the data that extensions process, in line with its broader commitment to privacy and openness within the web ecosystem.