Mozilla offers a standalone archive for Firefox on its official site - which keeps itself up to date automatically.
In a single human user context - working only from the relevant user session (so zero need for sudo, no system side mods):
⋅ unzip the standalone archive to a location in your $HOME (eg. ~/Software) and simply rename the resulting folder to firefox,
⋅ place in ~/.local/share/bin ( or ~/bin ) a symbolic link named firefox that targets the executable (eg /home/<your_name>/Software/firefox/firefox )
⋅ create in ~/.local/share/applications a launcher named firefox.desktop (a “short” version only french+english → here).
Relaunch your session: you should find Firefox in your usual applications menu but do not launch it yet.
In your desktop environment settings, find the equivalent of “Default Applications” and choose Firefox as your Internet Browser.
Launch Firefox, answer “Later” to the question “Do you want to make Firefox your default browser?” then in its settings, uncheck “Always check that Firefox is your default browser” - we have already checked this via “Default applications”
Otherwise on the one hand Firefox will ask you the question each time you launch it and on the other hand if you check it as the default browser from Firefox itself, it will create a second .desktop launcher with a random name, and add it as a duplicate in the mimeinfo.cache file.
In a multi-user context, it will be better to install this autonomous archive on the system side (therefore using sudo), e.g. in /opt/firefox with adequate management of rights and permissions so that the update mechanism can work from any session of a user who is a member of the users group.
⋅ unzip the standalone archive in /opt and simply rename the resulting folder to firefox
⋅ appropriate this firefox folder to root:users with rwxrwx— rights,
⋅ make sure that all the contents of this folder have root:users as owners BUT that only the folders carry the sgid bit with rwxrwx— rights via these 3 commands:
sudo chown -R root:users /opt/firefox/
sudo chmod 2770 /opt/firefox
find /opt/firefox/ -type d -exec sudo chmod 2770 {} \;
# you may replace 2770 by 2775 for any user to be able to launch Firefox,
# only members of users group will be able to update it.
⋅ place in /usr/bin a symbolic link named firefox which targets the executable ( here /opt/firefox/firefox )
⋅ create in /usr/share/applications a launcher named firefox.desktop (in long international version → there).
This way only users who are members of the users group can see, use and update the Firefox contained in /opt/firefox it is therefore imperative to add the concerned users to the users group via
sudo adduser user_A users
sudo adduser user_B users
or via a graphical utility like “Users and Groups” (provided by gnome-system-tools).
The same remarks apply concerning the default choice of browser, which can be refined with:
sudo update-alternatives --install /usr/bin/x-www-browser x-www-browser /usr/bin/firefox 100
and
xdg-settings set default-web-browser firefox.desktop