Add-on Policies

No Surprises

Users should be able to easily discern the functionality of your add-on based on the listing, and should not be presented with unexpected user experiences after installing it. The listing should include an easy-to-read description of what the add-on does, and what information it transmits. Please consult our best practices guide for creating an appealing listing.

Unexpected features

“Unexpected” features are those that are unrelated to the add-on’s primary function, and are not clearly indicated by the add-on name or description. This may include features that impact user privacy or security, make unexpected changes to web content, or change default settings like the new tab page, homepage, or search engine.

Any “unexpected” feature(s) must adhere to all of the following requirements:

• The add-on description must clearly state any changes made by these features.
• The features must be “opt-in”, meaning the user has to take non-default action to enact the change. Changes prompted by Firefox after the add-on is installed do not require an additional opt-in. The permissions prompt shown when installing an add-on does not alleviate the need for an opt-in.
• The opt-in interface must clearly state the name of the add-on requesting the change.

Content

Add-ons that make use of Mozilla trademarks must comply with the Mozilla Trademark Guidelines. If the add-on uses “Firefox” in its name, the naming standard the add-on is expected to follow is “<Add-on name> for Firefox”.

In addition, add-ons listed on addons.mozilla.org must adhere to the following policies:

• All add-ons submitted for listing on addons.mozilla.org are subject to Mozilla’s Acceptable Use Policy.
• Listings must disclose when payment is required to enable any add-on functionality.
• Add-ons and their content must conform to the laws of the United States. (Add-ons that violate or have content that violates the law in other jurisdictions may also be removed or have access limited.)
• If the add-on is a fork of another add-on, the name must clearly distinguish it from the original and provide a significant difference in functionality and/or code.
• Add-ons with the sole purpose of promoting, installing, loading or launching an outside website, application or add-on are not permitted.
• Themes that feature low-quality, stretched, or blank images, as well as those themes in which the header image is misaligned, are not permitted. Duplicate themes are not permitted.

Submission Guidelines

Add-ons must function only as described. During review, the add-on undergoes basic functional testing in addition to code review. To facilitate the functional testing, the add-on author must provide testing information and, if an account is needed for any part of the add-on’s functionality, testing credentials to allow use of the add-on.

If corrections have been requested and are submitted as part of a new version, the new version should not contain unrelated changes, as this complicates the review process and can lead to further delays or rejections.

Source Code Submission

Code must be provided in a way that is reviewable. Add-ons may contain transpiled, minified or otherwise machine-generated code, but Mozilla needs to review a copy of the source code before any of these steps have been applied.

The author must provide this information to Mozilla during submission along with instructions on how to reproduce the build. All dependencies must either be included in the source code package directly or downloaded only through the respective official package managers during the build process. Build tools or environments that no longer appear to be supported by their maintainers are not accepted. Reviewers may ask you to refactor parts of the code if it is not reviewable.

The provided source code is reviewed by an administrator and is not redistributed in any way. The code is only used for the purpose of reviewing the add-on. Failure to provide this information results in rejection or blocking.

Add-ons are not allowed to contain obfuscated code, nor code that hides the purpose of the functionality involved. If external resources are used in combination with add-on code, the functionality of the code must not be obscured. Minification of code with the intent to reduce file size is permitted.

Please read our Source Code Submission guidelines to avoid unexpected rejections or blocks.

Development Practices

In general, developers are free to maintain their add-ons in the manner they choose. However, in order to maintain appropriate data security measures and allow us to effectively review code, we have certain technical requirements that all add-ons must meet. In particular, potentially dangerous APIs may only be used in ways that are demonstrably safe, and code within add-ons that cannot be verified as behaving safely and correctly may need to be refactored.

The following requirements are of particular importance:

• Add-ons must only request those permissions that are necessary for them to function.
• Add-ons must be self-contained and not load remote code for execution.
• Add-ons must not load or redirect to a remote new tab page. The new tab page must be contained within the add-on.
• Add-ons must not relax web page security headers, such as the Content Security Policy.
• Add-ons must use encryption when transporting data remotely.
• Add-ons should avoid including redundant code or files.
• Add-ons must not negatively impact the performance or stability of Firefox.
• Only release versions of third-party libraries and/or frameworks may be included with an add-on. Modifications to these libraries/frameworks are not permitted. Please read our third party library guidelines to better understand related requirements.

Usage of the userScripts API is allowed for user script managers only. A user script manager is an extension that allows users to manage website-specific scripts. The userScripts API cannot be used to extend or modify the functionality of the user script manager itself. The user must:

• Proactively install a user script using an explicit action, for instance a click on a button labeled “Install this user script”.
• Be able to see which user scripts are currently installed and remove scripts without impacting the extension.

Data Collection and Transmission Disclosure and Control

Add-ons must limit data transmission to what is necessary for functionality, and must use the data only for the purpose for which it was transmitted. For the purposes of this policy, data transmission refers to any data that is collected, used, transferred, shared, or handled outside of the add-on or the local browser.

If the add-on uses native messaging, the Add-on Policies (including those related to user consent and control) apply to any data sent to the native application as well.

Prohibited Data Collection and Transmission

• Search functionality provided or loaded by the add-on must not transmit search terms or intercept searches that are going to a third-party search provider.
• Transmitting or facilitating the transmission of ancillary information (e.g. any data not required for the add-on’s functionality as stated in the description) is prohibited.
• The transmission of browsing activity is only permitted as part of the add-on’s primary function.

User Consent and Control

The user must be provided with a clear way to control the add-on’s data transmission, either through a consent experience created by the add-on developer, or by using Firefox’s built in data collection and transmission consent experience.

Add-ons installed in an enterprise environment can bypass asking for data collection consent when they are installed by enterprise policy. For more information, refer to the enterprise documentation. If the add-on uses Firefox’s built-in data collection and transmission consent experience, then the browser will bypass this by default.

If the add-on is only compatible with Firefox 140 or later and uses Firefox’s built-in data collection and transmission consent experience

It must accurately state the data collection practices in the extension manifest, including when it does not collect data, in line with the Firefox add-on data classification taxonomy.

If the add-on is compatible with Firefox 139 and earlier or uses Firefox’s built-in data collection and transmission consent experience

The user must be provided with a clear way to control the add-on’s data transmission immediately after installation of the add-on. If data transmission starts or changes in an add-on update, or the consent and control is introduced in an update, it must be shown to all new and upgrading users immediately after the update.

The data transmission consent and control must be contained within the add-on. The consent experience must:

• Be unmissable. It is recommended to present it in a new focused tab in the current window. Other ways that could be missed or accidentally hidden, like a popup window, will result in a rejection.
• Be presented on a single page, including all choices and decision options.
• Present users with a clear, readable data transmission consent. Information explaining the data transmitted must be prominently stated and not buried or hidden.
  • Avoid deceptive design patterns that make it harder to understand your data transmission policy, including, but not limited to, illegible font sizes, reduced color contrast, hidden options, multi-step consent decline flows, and similar techniques indicative of deceptive design.
• Clearly state what type of data is being transmitted.
• Inform about the impact of accepting or declining the data transmission

If both personal and technical data is being transmitted, the user must be provided separate choices. If the user declines the transmission, any resulting impact on their experience or use of the add-on must be limited to the data not being available.

Please refer to our best practices for advice and examples on how to design and implement a data transmission consent prompt.

Personal Data (opt-in)

Personally identifiable information can be actively provided by the user or obtained through extension APIs. It includes, but is not limited to names, email addresses, search terms and browsing activity data, as well as access to and placement of cookies.

Before an add-on may transmit personal information, it must clearly describe, and the user must affirmatively consent (i.e., explicitly opt-in) to the type of personal data being transmitted.

If the primary functionality of the add-on does not work without transmitting personal data, the add-on must provide a choice for the user to either accept the data transmission or uninstall the add-on.

Technical & User Interaction Data (opt-out)

Technical data describes information about the environment the user is running, such as browser settings, platform information and hardware properties. User interaction data includes how the user interacts with Firefox and the installed add-ons, metrics for product improvement, and error information.

When an add-on transmits either of these types of information, it must allow the user to disable that data transmission (opt-out) during the initial consent experience. The add-on functionality must not be restricted if the user declines transmission of this data.

Additional Privacy Protocols

• Leaking local or user-specific information to websites or other applications (e.g. through native messaging) is prohibited.
• Data from private browsing sessions must not be stored. Information that identifies a user across browsing sessions or containers must not be made available to web content.

Monetization

• An add-on injecting advertising into web page content must clearly identify the injected content as originating from the add-on.
• The inclusion of any cryptocurrency miners in an add-on is prohibited.
• Modifying web content or facilitating redirects to include affiliate promotion tags is not permitted. Conversely, the inclusion of affiliate promotions in user interface elements that are clearly identified as belonging to the add-on are acceptable.

Security, Compliance and Blocking

We expect all add-ons, whether hosted on addons.mozilla.org or not, to be secure and well-maintained in how they handle both their own data and their users’ data. They must also securely manage all of their interactions with the web and the browser and the operating system.

Policy Enforcement

Mozilla may reject or block affected versions or entire add-ons that don’t comply with the above policies, depending on the extent of their non-compliance.

Mozilla may attempt to contact the add-on’s developer(s) and provide a reasonable time frame for the problems to be corrected before a block is deployed. If an add-on appears to intentionally or repeatedly violate the policies, or its developers have proven unreachable, unresponsive, or uncooperative, blocking may be immediate.

Mozilla reserves the right to block or delete any developer’s account on addons.mozilla.org, thereby preventing further use of the service, for certain violations of Mozilla’s policies.

For more information about rejection and blocking, see What does review rejection mean to users?