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What Is a URL Slug?
A URL slug is the human-readable, URL-safe portion of a web address that identifies a specific page. For example, in https://example.com/blog/email-validation-guide, the slug is email-validation-guide. Slugs replace spaces with hyphens, remove special characters, and lowercase all letters.
Good slugs are short, descriptive, and contain primary keywords. They improve SEO because search engines use URL words as ranking signals, and they improve user experience because users can understand a page's content from its URL before clicking.
How Slug Generation Works
The slug generator transforms any text string into a clean, URL-safe slug.
- Lowercasing — converts all characters to lowercase
- Character replacement — replaces spaces and unsupported characters with hyphens
- Unicode transliteration — converts accented characters (café → cafe) and removes non-Latin characters
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Generate a Slug →When To Use Slug Generation
Slug generation is needed whenever user-provided text must become part of a URL.
- Blog posts — auto-generate URL slugs from post titles in CMS and blog platforms
- Product pages — create URL-safe identifiers from product names in e-commerce systems
- User profiles — generate username-based profile URLs from display names
Frequently Asked Questions
Should I use hyphens or underscores in URL slugs?
Hyphens are strongly preferred over underscores. Google treats hyphens as word separators (email-validator = two words: email, validator), while underscores join words into one token (email_validator = one word: emailvalidator). Using hyphens produces better keyword matching in search results.
How long should a URL slug be?
Shorter slugs are generally better for SEO and user experience. Aim for 3-5 keywords, roughly 50-60 characters. Very long slugs dilute keyword relevance and are harder to share. Avoid stop words (the, a, an, in, for) to keep slugs concise.
What happens when two pages have the same slug?
Duplicate slugs cause URL conflicts. CMS platforms typically handle this by appending a number (post-title-2, post-title-3). In code, always check for slug uniqueness before saving, and implement a collision resolution strategy in your slug generation logic.