Slug Validation Regex (URL Friendly)

Validate URL-friendly slugs with lowercase alphanumeric characters and hyphens using regex pattern.

Pattern Breakdown

^[a-z0-9]+(?:-[a-z0-9]+)*$

Components

Detailed Breakdown

• [a-z0-9]+ - First segment: must start with letter or digit
• (?:-[a-z0-9]+)* - Optional additional segments:
  • (?:...) - Non-capturing group
  • - - Literal hyphen separator
  • [a-z0-9]+ - One or more lowercase letters or digits
  • * - Zero or more occurrences

Examples

Valid:

• hello-world
• my-awesome-post
• article123
• test-slug-2024
• a
• 123abc

Invalid:

• Hello-World (uppercase not allowed)
• -hello-world (starts with hyphen)
• hello-world- (ends with hyphen)
• hello--world (double hyphen)
• hello world (spaces not allowed)
• hello_world (underscores not allowed)
• hello.world (dots not allowed)

Implementation

JavaScript

const slugRegex = /^[a-z0-9]+(?:-[a-z0-9]+)*$/;
slugRegex.test('hello-world'); // true
slugRegex.test('my-awesome-post'); // true
slugRegex.test('Hello-World'); // false (uppercase)
slugRegex.test('-hello-world'); // false (starts with hyphen)
slugRegex.test('hello--world'); // false (double hyphen)

Python

import re
slug_regex = r'^[a-z0-9]+(?:-[a-z0-9]+)*$'
bool(re.match(slug_regex, 'hello-world'))  # True
bool(re.match(slug_regex, 'my-awesome-post'))  # True
bool(re.match(slug_regex, 'Hello-World'))  # False (uppercase)

Go

slugRegex := regexp.MustCompile(`^[a-z0-9]+(?:-[a-z0-9]+)*$`)
slugRegex.MatchString("hello-world") // true
slugRegex.MatchString("my-awesome-post") // true
slugRegex.MatchString("Hello-World") // false (uppercase)

Limitations

1. Lowercase only: Only accepts lowercase letters
2. No underscores: Doesn't allow underscores
3. No special chars: Only hyphens allowed as separators
4. No length limit: Doesn't enforce maximum length
5. No reserved words: Doesn't prevent reserved slug names

When to Use

• URL slug generation and validation
• Blog post URLs
• SEO-friendly URLs
• Content management systems
• When you need clean, readable URLs

For production, consider:

• Adding maximum length validation
• Checking against reserved slug names
• Supporting case-insensitive matching
• Handling special characters by conversion
• Normalizing input before validation