advancedDocker Registry & Image Distribution: Tagging, Versioning, Push & Pull

Why does pushing a small code change to an image that shares a base with a previous version upload quickly?

Docker registries deduplicate by layer content digest — pushing only uploads layers that don't already exist in the registry, so a small change near the top of a well-ordered Dockerfile only re-uploads the changed layer(s), not the entire image.

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