docker system prune will delete ALL dangling data (i.e. In order: containers stopped, volumes without containers and images with no containers). Even unused data, with -a option.
You also have:
For unused images, use docker image prune -a (for removing dangling and ununsed images).
Warning: ‘unused‘ means “images not referenced by any container”: be careful before using -a.
As illustrated in A L‘s answer, docker system prune --all will remove all unused images not just dangling ones… which can be a bit too much.
Combining docker xxx prune with the --filter option can be a great way to limit the pruning (docker SDK API 1.28 minimum, so docker 17.04+)
The currently supported filters are:
until (<timestamp>)– only remove containers, images, and networks created before given timestamplabel(label=<key>,label=<key>=<value>,label!=<key>, orlabel!=<key>=<value>) – only remove containers, images, networks, and volumes with (or without, in caselabel!=...is used) the specified labels.
See “Prune images” for an example.