01
Read the first slash before the first colon
A host is recognized in the first segment when it contains a dot, colon or uppercase letter, or equals localhost. Without a slash, localhost is itself a Docker Hub repository name.
Docker & Containers
Docker image parsersee exactly what a reference selects
Parse one image reference or build it from separate fields. Inspect defaults and digest precedence before copying.
Docker image parser
Reference or fields
References stay in this browser. No registry lookup, upload or Docker daemon access.
Parsed reference
Enter a reference or repository path.
Input mode and examples
Modes keep separate drafts. Leave registry blank for Docker Hub; put the full repository path in its own field. A registry such as host:5000 is unambiguous.
One reference, up to 4,096 characters. Repository path: 255; tag: 128. Digests: sha256/384/512 with full lowercase hexadecimal.
Waiting to parse the latest input…
The Docker image parser helps when a deployment points somewhere unexpected. The colon in registry.example.com:5000/team/api:v2 separates a port in one place and a tag in another; splitting at the first colon loses that distinction.
Compare a short name with a private registry example. The result keeps the repository path and selector visible, so a missing host or an inherited latest tag does not disappear inside a string.
Why use this Docker image parser?
Make implicit defaults visible
The Docker image parser expands nginx to docker.io/library/nginx:latest. Default badges distinguish inserted values from the ones you supplied, while private registries keep their own repository paths.
Keep the tag without hiding the digest
A reference can contain both a tag and a digest. The normalized view preserves both for review, and a separate effective reference shows the digest-based selection without pretending the tag has been verified.
Avoid three common reference mistakes
02
Treat the two modes as separate drafts
Switching to fields preserves the text draft. In the builder, registry is optional and repository includes the namespace; do not append :tag or @digest to that field.
03
Check freshness before taking the result
Auto parsing waits 350 ms. Turn it off to reveal the run button; Ctrl/Cmd + Enter also runs. Loading examples and clearing show a replacement preview, and one undo restores the input and result.
Inspect a reference from host to content selector
Resolve Docker Hub shorthand
The container image parser applies docker.io and library only where Docker shorthand calls for them. It also maps index.docker.io to docker.io, while leaving tag case intact and refusing uppercase repository paths.
Validate each component separately
A Docker image reference can contain a hostname, numeric port or bracketed IPv6 registry. Repository separators, tag characters and digest lengths are checked independently, so a malformed digest is not mistaken for a version label.
Build and export the same interpretation
Combine registry, repository, tag and digest fields into a named reference. Copy the normalized or effective string, or export JSON with the parsed fields and default flags. Export stays disabled after an edit until the current draft succeeds.
What acceptance does and does not mean
- Syntax does not prove availability
- No image is fetched and no registry, permission, manifest, architecture, signature or vulnerability is inspected. Building here means composing a reference string, not building an image or running a Docker command.
- Selectors are not interchangeable
- latest is added only when both tag and digest are absent. A digest takes precedence over a supplied tag; the tool neither resolves tags to digests nor confirms that the two select the same image.
- Named references only
- Paste one bare reference, not a Dockerfile, Compose document, URL, shell command, image archive or list. Outer whitespace is trimmed; internal whitespace, credentials and unresolved variables are rejected. Bare image IDs are not resolved.
- Explicit grammar and size limits
- Active input is limited to 4,096 characters and the normalized repository path to 255. Tags allow 1–128 ASCII letters, digits, underscores, dots and hyphens, with no leading dot or hyphen. Only full lowercase sha256/384/512 digests are supported. IPv6 zone IDs and dotted IPv4-in-IPv6 forms are rejected; numeric ports are not tested for reachability.
Docker image parser questions
Why does Docker say the repository name must be lowercase?
Repository path components must be lowercase; tag text may contain uppercase letters. Check the namespace and image name before the tag separator. This tool flags the path rather than silently changing it, because a typo could name a different target.
Does Docker check that a supplied tag matches the digest?
Do not rely on that check. When both are supplied, the digest controls selection. The normalized output keeps the original tag for inspection, while the effective output omits it. Confirm any claimed relationship with registry metadata separately.
How can I tell which version latest points to?
The word latest is a tag, not a request to calculate the newest semantic version. Its owner chooses what it points to and can move it. This parser shows the tag literally; finding its current digest requires a registry query outside this tool.
Why does a local registry reference point at docker.io?
In registry/api, the lowercase first segment lacks a dot or port and is treated as a namespace. Try registry:5000/api or an appropriate dotted host. The builder rejects an ambiguous registry field instead of quietly producing a Docker Hub target.
What is the difference between an image ID and a digest?
An image ID identifies local image configuration content; a registry digest may identify a manifest or an image index. They are not generally the same hash. Supply a repository followed by @ and its registry digest; this tool cannot derive one identifier from the other.
Still have a question?
Review your next reference
Use the Docker image parser to check the destination and selector together. Take the effective reference only after the current draft has passed validation.