Toolkit
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.
The management and update windows for extensions and themes (add-ons).
Application update for Firefox, Thunderbird, and Sunbird.
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.
Breakpad crash reporting library - exception handler and crash report sender application.
For bugs in Toolkit build and config
Bugs and feature requests for Firefox downloading.
The Error Console displays errors, warnings and messages from various components including but not limited to JavaScript, DOM, XML, and CSS. This component is for problems with the Console itself and not for browser or web page problems that are noted in the console.
Find as you Type/Find Toolbar
Bugs and feature requests for the Forget About This Site feature.
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
Popup/doorhanger notifications, notification bars, alerts, and prompts.
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
Remembers usernames and passwords on sites and fills them when the user returns to the site. Debug Logging can help diagnose problems.
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.
The component for displaying pages in a special reader mode. Includes about:reader page and Readability article-parsing library.
Safe Browsing UI and service (includes phishing protection).
For toolkit security bugs.

If the problem relates to underlying components (PSM, NSS, Core), or a specific product built upon toolkit and not this layer then please file it in the appropriate product instead of here.

Spatial navigation allows you to change the focus of a web page using directional keys (Up, Down, Left, Right).
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.
Widgets for toolbar display and customization.
For problems related to the default controls used in HTML 5 media elements (<video> and <audio>).
For issues concerning the source window for web pages.
File feature requests and bugs related to the WebExtension add-on API.
For bugs in widgets implemented by the XUL Toolkit