The container technology has the purpose of being available in different environments where necessary. As a result, the applications are rebuilt on launch.

As containers, networks, volumes or images that are no longer used are nevertheless saved, this can easily take up a few GB, depending on the size of the applications. 

You can remove the corresponding data using the following commands (only data that has no relation to the currently running applications is removed):

This is how you can check how much storage space can be released:

docker system df

Remove all images:

docker image prune 

Remove all containers:

docker container prune 

Remove all networks

docker network prune 

Remove everything:

docker system prune

You can find more information in the official Docker documentation under Pruning