I was recently pointed out by Piotr Gabryjeluk that Iceweasel name was dropped (see Debian Bug report #815006). This caused a major inconsistency in the previous blog post.

This is an updated version for Debian Jessie

First step

Add GnuPG archive key for mozilla.debian.net repository to the list of trusted keys.

$ wget -q -O - http://mozilla.debian.net/archive.asc | \
  sudo apt-key add -

Second step

Add the desired repository to the active APT data sources.

Release version

$ cat << EOF | sudo tee /etc/apt/sources.list.d/mozilla-firefox.list
deb http://mozilla.debian.net/ jessie-backports firefox-release
EOF

Beta version

$ cat << EOF | sudo tee /etc/apt/sources.list.d/mozilla-firefox.list
deb http://mozilla.debian.net/ jessie-backports firefox-beta
EOF

Aurora version

$ cat << EOF | sudo tee /etc/apt/sources.list.d/mozilla-firefox.list
deb http://mozilla.debian.net/ jessie-backports firefox-aurora
EOF
You can find a basic version comparison at the bottom of this article.

Third step

Assign higher priority to the recently added repository.

$ cat << EOF | sudo tee /etc/apt/preferences.d/mozilla-firefox
Package: *
Pin: origin mozilla.debian.net
Pin-Priority: 501
EOF

Fourth step

Update package index.

$ sudo apt-get update

Fifth step

Verify assigned priorities.

$ apt-cache policy firefox
firefox:
  Installed: (none)
  Candidate: 45.0.1-1~bpo80+1
  Version table:
     45.0.1-1~bpo80+1 0
        501 http://mozilla.debian.net/ jessie-backports/firefox-release amd64 Packages

Sixth step

Install the Firefox browser.

$ sudo apt-get install firefox

Do not worry about Iceweasel. It is better to just ignore it for a while as the situation will stabilize soon. [I am thinking about dependencies.]

Ending notes

Project website

Please visit the Debian Mozilla team website for more information and use the repository wizard.

Version comparison

$ apt-cache policy firefox
firefox:
  Installed: (none)
  Candidate: 47.0~a2+20160318004008-1~bpo80+1
  Version table:
     47.0~a2+20160318004008-1~bpo80+1 0
        501 http://mozilla.debian.net/ jessie-backports/firefox-aurora amd64 Packages
     46.0~b2-1~bpo80+1 0
        501 http://mozilla.debian.net/ jessie-backports/firefox-beta amd64 Packages
     45.0.1-1~bpo80+1 0
        501 http://mozilla.debian.net/ jessie-backports/firefox-release amd64 Packages