What characters are allowed in a Docker tag?

A tag may contain lowercase and uppercase letters, digits, underscores, periods and hyphens, up to 128 characters, and may not start with a period or hyphen. This tool only emits characters from that set so every generated tag is valid for docker push.

Why combine a version with a git hash?

A tag like 1.4.0-a1b2c3d ties a human-readable release to the exact commit it was built from. It stays readable for humans while remaining traceable, which is a common immutable-tag convention in CI pipelines.

Should I rely on the latest tag?

Generally no. The latest tag is mutable and points at whatever was pushed most recently, which makes deployments non-reproducible. Prefer an immutable tag such as a version or a git sha, which is why this tool favours those styles.

What does the timestamp style produce?

It emits a sortable UTC stamp such as 20260606-1430, optionally combined with a short hash. Timestamp tags are useful for nightly or continuous builds where there is no formal version bump.

Is anything sent to a server?

No. All tags are produced locally in your browser with no network requests, so the tool works offline and nothing you generate leaves your machine.

Docker Tag Generator

Build tags your registry will accept

The Docker Tag Generator produces image tag strings that follow Docker’s tag grammar and common CI conventions. Pick a style — semantic version, short git hash, the two combined, or a timestamp — add an optional environment suffix, and get tags you can drop straight into a docker build -t command or a pipeline script.

How it works

Docker restricts a tag to letters, digits, underscores, periods and hyphens, with a 128-character limit and no leading period or hyphen. The generator builds each tag from those characters only. A semver core is MAJOR.MINOR.PATCH; a git-style identifier is a seven-character lowercase hex string mimicking an abbreviated commit SHA; a timestamp is a sortable YYYYMMDD-HHMM stamp.

The combined version-sha style joins a release with its source commit (for example 1.4.0-a1b2c3d) so the tag is both readable and immutable. An optional environment suffix such as -staging records the build target. Because mutable tags like latest defeat reproducible deploys, the tool deliberately produces immutable, content-anchored tags instead.

Tips and example

For release builds use the version or version-sha style: 2.0.1 or 2.0.1-9f3c0de.
For per-commit CI builds use the git-sha style so each push gets a unique, immutable tag.
For nightly builds use the timestamp style: 20260606-0300.
Keep tags lowercase by convention even though uppercase is technically allowed — many tools and humans expect it.
All hashes and stamps are synthetic; never treat a generated tag as a real build artifact.