A URL slug is the part of a web address that comes after the domain name and identifies a specific page in a human-readable format. For example, in the URL "example.com/blog/what-is-url-shortening," the slug is "what-is-url-shortening." Slugs are typically generated from page titles by converting to lowercase, replacing spaces with hyphens, and removing special characters.
URL slugs play a critical role in SEO because search engines use them as signals to understand page content. A descriptive slug that includes relevant keywords can improve a page's visibility in search results. Google's documentation explicitly recommends using simple, descriptive URLs that convey the page's topic. SEO fundamentals books on Amazon cover these principles.
In URL shortening services, the slug concept applies to custom aliases. When a user creates a short URL with a custom code, that code functions as the slug for the shortened link. The same best practices apply: keep it concise, use meaningful words, and avoid special characters.
Slug generation algorithms must handle edge cases such as duplicate titles, non-ASCII characters, and reserved words. Unicode slugs require transliteration or encoding decisions that vary by platform and target audience. Web development books on Amazon discuss internationalization challenges.