For bugs in Firefox Desktop, the Mozilla Foundation's web browser. For Firefox user interface issues in menus, bookmarks, location bar, and preferences. Many Firefox bugs will either be filed here or in the Core product. Bugs for developer tools (F12) should be filed in the DevTools product. (more info)
For issues dealing with helper applications, and guessing Content Types when they aren't specified/known (ftp:, file:, jar:, but generally not http:). This component does not cover: backend networking issues, such as those covered by Networking: FTP or Networking: File, nor does it cover the Download Manager which has its own component in the Toolkit product.