compton software package provides compositor for X11, based on xcompmgr, 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 compton
compton is installed in your system.
Make ensure the compton package were installed using the commands given below,
$ sudo dpkg-query -l | grep compton *
You will get with compton package name, version, architecture and description in a table
| Distro | Debian 9 stretch |
| Section | X Window System software |
| Package | compton |
| Version | 0.1~beta2+20150922-1 |
| Description | compositor for X11, based on xcompmgr |
| Sub Section | x11 |