Download Firefox Full Version For All languages And Systems {web link} Save the file. Then;

Using your file browser, open the Programs Folder on your computer.

Windows: C:\Program Files C:\Program Files (x86) Mac: Open the "Applications" folder. Linux: Check your user manual.

• Linux: If you installed Firefox with the distro-based package manager, you should use the same way to uninstall it - see Install Firefox on Linux. If you downloaded and installed the binary package from the Firefox download page, simply remove the folder Firefox in your home directory.

Now run the full version.

Removed comment that will have inexperienced users removing their Profiles.

If there are problems with updating or with the permissions then best is to download the full version and trash the currently installed version to do a clean install of the new version.

Download a new copy of the Firefox application and save the disk image file to the desktop

• Firefox 39.0: https://www.mozilla.org/en-US/firefox/all/

• Trash the current Firefox application (open the Applications folder in the Finder and drag the Firefox application to the Trash) to do a clean (re)install
• Install the new version that you have downloaded
• https://support.mozilla.org/kb/Installing+Firefox+on+Mac

Your personal data is stored elsewhere in the Firefox profile folder, so you won't lose your bookmarks and other personal data when you uninstall and (re)install or update Firefox.

• http://kb.mozillazine.org/Profile_folder_-_Firefox

MalMcKay said

Why have I been asked, and complied to download 39.0 at least 7 times. My version though is 38.0.5 It doesn't seem to update. Also, why for the last twelve months been losing my cursor when I am in the top half of the screen. I've been to Apple. The problem only happens in my Firefox Browser. Devoted Firefox user Hugs, Mal Malcolm Mckay

Thank you. It worked well. Hugs, Mal

Glad to help. Safe Surfing.