firefox-esr software package provides Mozilla Firefox web browser - Extended Support Release (ESR), you can install in your Debian 9 (Stretch) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install firefox-esr
firefox-esr is installed in your system.
Make ensure the firefox-esr package were installed using the commands given below,
$ sudo dpkg-query -l | grep firefox-esr *
You will get with firefox-esr package name, version, architecture and description in a table
| Distro | Debian 9 stretch |
| Section | Web Software |
| Package | firefox-esr |
| Version | 45.4.0esr-2 |
| Description | Mozilla Firefox web browser - Extended Support Release (ESR) |
| Sub Section | Web |