The Mozilla Toolkit is a set of APIs, built on top of Gecko, which provide advanced services to XUL applications. These services include Profile Management, Chrome Registration, Browsing History, Extension and Theme Management, Application Update Service, and Safe Mode. (More info)

Select a component to see open bugs in that component:


This component implements Firefox's about:memory page.

Add-ons Manager

The management and update windows for extensions and themes (add-ons).

Application Update

Application update for Firefox and Thunderbird.

Async Tooling

Tools designed for writing asynchronous code. This includes Promise.jsm, Task.jsm, AsyncShutdown, as well as Chrome Worker modules that do not have their own component.


Auto-completing text entry widget.


Requests to blocklist an add-on, plugin, or other third party component. Please read our policies first.

Build Config

For bugs in Toolkit build and config

Crash Reporting

Breakpad crash reporting library - exception handler and crash report sender application.

Downloads API

For issues relating to the process of downloading files to disk, including for example progress calculation and timing, folder choice, file naming, and file system access. Does NOT cover: - The user interface (see Firefox :: Downloads Panel) - Networking issues (see Core :: Networking) - Choosing the handler application (see Firefox :: File Handling) - Saving complete web pages (see Firefox :: File Handling)

Find Toolbar

Find as you Type/Find Toolbar

Forget About Site

Bugs and feature requests for the Forget About This Site feature.

Form Manager

The component that captures user data appearing on a form and autofills that data on other forms.


For bugs in Toolkit code that don't fit into any of the other components.


Microformats API for toolkit-based applications

Notifications and Alerts

Popup/doorhanger notifications, notification bars, alerts, and prompts.

NSIS Installer

General NSIS Installer bugs.


For bugs in Mozilla's JavaScript OS.File module. This does not cover the DOM File API. If you are filing a bug related to file I/O but you are not sure whether the underlying module is OS.File, please use component Networking: File

Password Manager

Remembers usernames and passwords on sites and fills them when the user returns to the site. Debug Logging can help diagnose problems.

Password Manager: Site Compatibility

Reports of password manager not working on a specific site. Generic heuristic improvements should be filed in Toolkit::Password Manager. Debug Logging can help diagnose problems. A URL should be specified in the URL field.

Performance Monitoring

Tools for monitoring the performance of the platform, add-ons and webpages. Such monitoring includes speed, jank, memory usage.


Manages the user's history, bookmarks, livemarks and annotations. This component is for bugs in the Places APIs, database tables, and code used to access Places data.


Preference UI and widgetry.


Print Preview and other toolkit elements of printing.

Reader Mode

The component for displaying pages in a special reader mode. Includes about:reader page and Readability article-parsing library.

Safe Browsing

Safe Browsing UI and service (includes phishing protection).

Startup and Profile System

New applications startup system - including shared AppRunner, AppStartup, and profile system.


SQLite-backed generic data storage and query engine.


Telemetry allows Engineering to receive aggregate data of browser health in the field.


General user interface, user experience, and visual design for the default theme used in Toolkit components.

Toolbars and Toolbar Customization

Widgets for toolbar display and customization.

Video/Audio Controls

For problems related to the default controls used in HTML 5 media elements (<video> and <audio>).

View Source

For issues concerning the source window for web pages.

WebExtensions: Android

Bugs about WebExtensions on Android.

WebExtensions: Compatibility

Compatibility with other browsers, including advocacy for add-ons we'd like to support.

WebExtensions: Developer Tools

Bugs about debugging, reloading add-ons, error messages and devtools APIs.

WebExtensions: Experiments

Experiments and new APIs for WebExtensions.

WebExtensions: Frontend

Bugs about front end APIs and interaction such as buttons, tabs, windows, popups.

WebExtensions: General

All other bugs about WebExtensions

WebExtensions: Request Handling

Bugs about request handling including webRequest and webNavigation.

WebExtensions: Untriaged

File feature requests and bugs related to the WebExtension add-on API.

WebPayments UI

User Interface for the WebPayments Payment Request API and Payment Handler API.

XUL Widgets

For bugs in widgets implemented by the XUL Toolkit