What Is a URL Slug?

A URL slug is the part of a web address that comes after the domain name, identifying a specific page. A clean slug is short, readable, and descriptive of the page’s content, rather than a string of numbers or parameters.

Why the URL slug matters

A clean slug tells both users and search engines what a page is about before anyone even clicks, and it stays readable when shared or pasted elsewhere, in an email, a text message, a printed document. A messy, parameter-heavy URL like /page?id=4821&cat=12 gives none of that context and looks untrustworthy to a cautious clicker. The slug’s SEO value is genuinely modest compared to content quality or backlinks, but it’s one of the few on-page elements you set once and essentially never have to think about again, cheap to get right upfront.

How to write a good URL slug

1. Keep it short. Fewer words are easier to read, share, and remember, and shorter URLs correlate with (though don’t cause) better performance in some studies.
2. Use hyphens between words, not underscores or spaces, hyphens are treated as word separators by search engines, underscores aren’t.
3. Include the primary keyword where it fits naturally, without forcing every secondary term into the URL.
4. Remove stop words like “a,” “the,” and “of” unless they’re needed for readability or meaning.
5. Avoid dates and version numbers in evergreen content slugs, since they make otherwise-current content look outdated even after an update.

Common URL slug mistakes

• Changing slugs without redirecting. This breaks every existing backlink and bookmark pointing to the old URL, and can tank rankings if not paired with a proper 301 redirect.
• Overly long, keyword-stuffed slugs. Cramming every target keyword into the URL reads as spammy and doesn’t meaningfully outperform a shorter, clear version.
• Using default auto-generated IDs. Some CMS platforms default to numeric or parameter-based URLs unless manually overridden.
• Inconsistent casing or special characters. Mixed case, spaces, or unusual symbols can create duplicate-content issues if both versions of a URL become accessible.

Good vs. weak URL slugs

Real example

For example, in the URL yoursite.com/best-running-shoes-2026, the slug is “best-running-shoes-2026,” a clean, readable summary rather than something like /page?id=4821, which conveys nothing about the page’s actual content to a person glancing at the link.

URL slugs and AI search

A clear, descriptive URL slug provides an additional, if minor, contextual signal for AI systems attempting to understand and categorize a page alongside its actual content, similar to how it aids traditional crawlers. It’s a small piece of a much larger picture, but a readable slug costs nothing and adds one more consistent, human-readable signal to the overall page context an AI system evaluates.

FAQ

Should I change an old, ugly URL slug to improve SEO?

Only with a proper 301 redirect from the old URL to the new one, and generally only if the page isn’t already ranking well, since the change itself carries some risk without a clear, larger benefit.

Do numbers or dates in a slug hurt SEO?

Not directly, but a specific year in an evergreen content slug can make the page look outdated to searchers even after you’ve updated the content, worth avoiding for content meant to stay relevant long-term.

Are hyphens or underscores better in a URL slug?

Hyphens. Google explicitly treats hyphens as word separators; underscores are read as connecting the words into a single string, hurting keyword recognition.

How long should a URL slug be?

As short as possible while remaining clear and descriptive, generally a handful of words. There’s no strict limit, but shorter, cleaner slugs are consistently easier to read and share.

Related terms

• 301 redirect
• Title tag
• Site architecture

Set the slug right the first time, changing it later always carries risk. A clean URL costs nothing upfront and saves you a redirect headache down the line.