How to delete all unused Docker container images

Over time my local development machine gets messy with a lot of container images I've built, tested but never deleted. This can consume a lot of hard disk. With some containers still running it's not easy to see within 1 second what to delete and what not.

Luckily there's a nice Docker command to check your system and clean it up. With docker system df you get a summary of your current usage:

❯ docker system df
TYPE            TOTAL     ACTIVE    SIZE      RECLAIMABLE
Images          48        9         25.8GB    25.35GB (98%)
Containers      22        0         3.321GB   3.321GB (100%)
Local Volumes   10        10        4.726GB   0B (0%)
Build Cache     0         0         0B        0B

Delete dangling images

With a quick docker image prune you can clean up your system. The command deletes all dangling images. Dangling images are images which are not in use by any container or are untagged.

docker image prune

WARNING! This will remove all dangling images.
Are you sure you want to continue? [y/N] y

To bypass the Warning question you can pass -f or --force.

Delete all unused images

To remove all images that are not referenced by an existing container, not just the dangling ones, use the prune command with the -a flag:

docker image prune -a

Using filters

The docker image prune command also allows you to remove images based on a condition using the --filter flag.

As of this writing the currently supported filters are until and label. You can use more than one filter by using multiple --filter flags.

For example, if you want to remove all images that were created more than 24 hours ago, you can run the following command:

docker image prune -a --filter "until=24h"