In April 2025, I’ll be in Paris at DevoxxFR to present a talk, in French, “Manifests, blobs and tags: container images finally digest(ible)”.

This is an updated version of the one I gave at Dockercon.

For some time now, containers and their images have been everywhere, on development machines, in production systems, or simply as a means of packaging. But what exactly is an OCI (Open Container Initiative) image?

In this session, we’ll explore, in the most interactive way possible, what an image really is:

• What makes an image, an image?
• How do you pull or push an image?
• What exactly is a blob? And what is a manifest?
• And what about tags and digests?
• My image runs on both amd64 and arm64: how is that possible?
• Can we go further? Can we store something else in an image? Or even extend it?

Let’s embark on a step-by-step journey into the world of images: we’ll create an image using existing tools, and then dissect it. And by the end, you might even come away with ideas for new tools to leverage this format, which is far more flexible than it might appear at first glance.