How a URL slug works
The slug is the part of a web address that identifies one page: everything after the domain and any folder path. In a content management system it is usually generated from the page title and then edited. Lowercase words separated by hyphens is the convention, because hyphens are read as word breaks while underscores are not, and because some servers treat uppercase and lowercase as two different addresses.
A slug is a small ranking signal and a large usability one. Search engines can read the words in it, but the bigger effect is on people. An address that describes the page is easier to trust in a set of results, easier to read when pasted into a message, and easier to repeat out loud over the phone.
Why the URL slug matters
Addresses are the one part of a site that is expensive to change. Every link anyone has ever made to a page, every bookmark, every directory citation points at the address as it was. Changing it means redirects, and redirects mean maintenance, so the cheapest moment to get a slug right is before publishing.
The words also set expectations. An address that reads as a service and a place tells a searcher what they are about to open before they click; a string of identifiers and query parameters tells them nothing, and looks generated rather than written.
Common mistakes with URL slugs
Dates in the path are the classic. An address stamped with the year it was written makes a genuinely updated article look stale, and moving away from that structure later means redirecting an entire archive.
Stuffing is the other extreme: an address repeating a term several times in the hope of relevance. It reads as spam, and long addresses are truncated in results and mangled when shared.
Then there is drift. A page is renamed, the system quietly generates a new address, and the old one either breaks or is redirected without anyone updating the internal links pointing at it — leaving every link on the site taking a detour. Editing a slug after publication is a decision, not a tidy-up, and it needs a permanent redirect and a pass over the links behind it.
How to act on it
Write the slug deliberately when you create the page. Use a few real words that describe it, drop filler such as “and”, “the” and “for” where they add nothing, keep it lowercase and hyphenated, and leave out the year, the category name and any words already implied by the folder it sits in. Shorter is better as long as it still reads.
Keep the pattern consistent across a section so addresses are predictable, and settle the structure once, before a hundred pages exist. If you must change a slug, redirect the old address to the new one, update the internal links to point straight at the destination rather than through the redirect, and check that your sitemap and any campaign links use the final address. Reviewing addresses alongside titles and headings is part of routine on-page SEO.