Myth: Deleting a Tag Deletes the Image from the Registry

During a production vulnerability cleanup, a team deleted the v1.0.1 tag from Docker Hub after a critical CVE was discovered. The assumption was simple:

“The image is deleted, no one can pull it anymore.”

A week later, during a rollback incident, an engineer pulled the same image using its digest and redeployed it successfully.

The image was never gone.

Why This Myth Exists?

1. Tag-centric mental model

Most engineers equate repo:tag with the image itself.

2. Registry UI abstraction

Docker Hub and other registries show tags as “images,” hiding the underlying content-addressable model.

3. Hidden garbage collection

Users rarely understand when (or if) garbage collection runs.

4. Docker CLI behavior

Commands like docker pull nginx:1.25 reinforce the idea that tags are the image.

The Reality

OCI registries are content-addressable storage systems.

• Tags are references, not the artifact

• Digests identify the actual artifact

• Deleting a tag only removes a pointer

• The underlying blobs and manifest remain until:

  • No references exist and
  • Garbage collection runs

• As long as the digest exists, the artifact exists.

Experiment & Validate

Step 1: Verify image exist with single tag

Step 2: Delete a tag from Dockerhub

• Go to Docker Hub
• Navigate to the repository
• Note the image digest
• Delete the v10 tag

At this point, the UI shows the image as deleted.

Step 3: Pull Image with digest

Output:

docker.io/rajeshd2090/busy@sha256:895ab622e92e18d6b461d671081757af7dbaa3b00e3e28e12505af7817f73649: Pulling from rajeshd2090/busy
ee153a04d683: Pull complete 
Digest: sha256:895ab622e92e18d6b461d671081757af7dbaa3b00e3e28e12505af7817f73649
Status: Downloaded newer image for rajeshd2090/busy@sha256:895ab622e92e18d6b461d671081757af7dbaa3b00e3e28e12505af7817f73649
docker.io/rajeshd2090/busy@sha256:895ab622e92e18d6b461d671081757af7dbaa3b00e3e28e12505af7817f73649

Key Takeaways

• In OCI registries, deleting a tag is not enough. Garbage collection is the only way to completely remove an artifact.
• Tags are mutable references, not artifacts
• Digests are the true identity of OCI artifacts
• Deleting a tag does not guarantee artifact removal
• Vulnerable or deprecated images may still be retrievable
• Registry garbage collection is delayed, vendor-specific, and opaque