What is the regex for docker image tag?

The regex pattern for docker image tag is `^(?:[a-z0-9]+(?:[._-][a-z0-9]+)*\/)*[a-z0-9]+(?:[._-][a-z0-9]+)*(?::[a-zA-Z0-9._-]+)?$`. This pattern validates docker image name with optional registry and tag.

How do I use this regex in JavaScript?

In JavaScript, create the regex with `const regex = /^(?:[a-z0-9]+(?:[._-][a-z0-9]+)*\\/)*[a-z0-9]+(?:[._-][a-z0-9]+)*(?::[a-zA-Z0-9._-]+)?$/;` and test with `regex.test(yourValue)`. It returns `true` if the value matches.

How do I use this regex in Python?

In Python, use `import re; re.match(r'^(?:[a-z0-9]+(?:[._-][a-z0-9]+)*\/)*[a-z0-9]+(?:[._-][a-z0-9]+)*(?::[a-zA-Z0-9._-]+)?$', value)`. The raw string prefix (`r`) prevents Python from interpreting backslashes as escape characters.

Is this regex case-sensitive?

By default, yes. To make it case-insensitive, add the `i` flag in JavaScript (`/^(?:[a-z0-9]+(?:[._-][a-z0-9]+)*\/)*[a-z0-9]+(?:[._-][a-z0-9]+)*(?::[a-zA-Z0-9._-]+)?$/i`) or use `re.IGNORECASE` in Python.

Regex for Docker Image Tag

Regex Pattern

^(?:[a-z0-9]+(?:[._-][a-z0-9]+)*\/)*[a-z0-9]+(?:[._-][a-z0-9]+)*(?::[a-zA-Z0-9._-]+)?$

Docker image name with optional registry and tag

Quick Answer

The regex pattern for docker image tag is `^(?:[a-z0-9]+(?:[._-][a-z0-9]+)*\/)*[a-z0-9]+(?:[._-][a-z0-9]+)*(?::[a-zA-Z0-9._-]+)?$`. Docker image name with optional registry and tag. This works in JavaScript, Python, Ruby, PHP, Java, and most regex engines that support PCRE syntax.

Test Examples

Input	Result
nginx:latest	✓ Matches
my-registry.com/my-app:v1.0	✓ Matches
ubuntu:22.04	✓ Matches
NGINX:latest	✗ No match
:latest	✗ No match
/invalid	✗ No match

Code Examples

javascript

const regex = /^(?:[a-z0-9]+(?:[._-][a-z0-9]+)*\\/)*[a-z0-9]+(?:[._-][a-z0-9]+)*(?::[a-zA-Z0-9._-]+)?$/;
const isValid = regex.test(value);

python

import re
pattern = r'^(?:[a-z0-9]+(?:[._-][a-z0-9]+)*\/)*[a-z0-9]+(?:[._-][a-z0-9]+)*(?::[a-zA-Z0-9._-]+)?$'
if re.match(pattern, value):
    print("valid")

ruby

pattern = /^(?:[a-z0-9]+(?:[._-][a-z0-9]+)*\/)*[a-z0-9]+(?:[._-][a-z0-9]+)*(?::[a-zA-Z0-9._-]+)?$/
if value =~ pattern
  puts "valid"
end

php

if (preg_match('/^(?:[a-z0-9]+(?:[._-][a-z0-9]+)*\\/)*[a-z0-9]+(?:[._-][a-z0-9]+)*(?::[a-zA-Z0-9._-]+)?$/', $value)) {
    echo "valid";
}

java

String pattern = "^(?:[a-z0-9]+(?:[._-][a-z0-9]+)*\\/)*[a-z0-9]+(?:[._-][a-z0-9]+)*(?::[a-zA-Z0-9._-]+)?$";
boolean isValid = value.matches(pattern);

Frequently Asked Questions

Related Regex Patterns

JavaScript Variable Name

Valid JavaScript variable/identifier name

Python Variable Name

Valid Python identifier name

CSS Class Name

Valid CSS class name (starts with letter, underscore, or hyphen)

CSS ID Selector

CSS ID selector starting with #

JSON Key

JSON object key (quoted string followed by colon)

Semantic Version (Strict)

Strict semantic versioning (MAJOR.MINOR.PATCH)