What is a URL slug?
A slug is the human-readable part of a URL that identifies a specific page — the words after the final slash in an address like /blog/how-to-format-json. A slug generator converts a title or headline into that form by lowercasing the text, stripping accents and punctuation, and replacing spaces with single hyphens, producing a clean, predictable path segment.
Slugs matter because a URL is not just plumbing; it is content that both people and search engines read. A descriptive slug tells a visitor what a link leads to before they click, and it survives being copied into emails, chats, and documents far better than a string of query parameters or random characters. In that sense a slug is a small piece of user experience as much as it is a technical detail.
Slugs and SEO
Search engines use the words in a URL as one of many relevance signals, so a concise slug that contains the page's core keywords reinforces what the content is about. Hyphens are the right separator because search engines treat them as spaces between distinct words, whereas underscores are not, and spaces are not valid in a clean URL at all.
Keep expectations realistic: a good slug is a small optimization, not a ranking silver bullet. It will not lift weak content, but combined with strong material it improves clarity, click-through from search results, and how shareable your links feel. Search engines are increasingly good at understanding a page regardless of its URL, so treat the slug as helpful reinforcement of your topic rather than the thing your ranking depends on.
Transliteration, normalization, and uniqueness
Turning free text into a safe slug involves more than replacing spaces. Accented and non-Latin characters are normalized toward their base ASCII letters — é becomes e, ü becomes u — so the slug stays portable across systems that mishandle unicode in URLs, and stray symbols are removed entirely.
One thing a generator cannot decide for you is uniqueness. Two different articles titled the same way produce the same slug, so a content system typically appends a number or an identifier to avoid collisions. Standardizing slugs up front, then handling duplicates consistently, keeps redirects, analytics, and internal linking manageable as a site grows to thousands of pages. A little discipline early — consistent casing, sensible length, and a clear duplicate strategy — pays off as content and traffic accumulate over the years. The goal is a URL you would be comfortable reading aloud, and that standard tends to produce good results for both people and search engines.