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What is a Docker image tag?

DockerJunior~1 min read
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A Docker image tag is a label assigned to an image to distinguish its versions. Usually the tag is used as a human-readable version name, for example: latest, 1.0, dev, prod.

What a tag looks like

bash
nginx:1.25 python:3.10 myapp:latest

Where:

  • nginx, python, myapp - the image name
  • 1.25, 3.10, latest - the tag

Why a tag is needed

  • to keep multiple versions of the same image;
  • so that deployment, testing, and development work predictably;
  • so you can roll back to a specific version.

A detail worth noting

If no tag is specified, Docker defaults to :latest.

Summary: a tag is a version or label of an image that helps distinguish variants of the same Docker image.

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