Slugify — URL Slug Generator

What a slug is and why it matters

A slug is the human-readable part of a web address that identifies a specific page, the how-to-bake-bread in example.com/blog/how-to-bake-bread. It is the difference between a URL a person can read, trust, and remember and one made of opaque numbers or query strings. A slugify tool converts a title or heading into that form by lowercasing the text, replacing spaces with a separator, stripping characters that are unsafe or meaningless in a URL, and converting accented letters to plain ASCII.

Slugs matter for more than tidiness. A descriptive slug tells both readers and search engines what a page is about before they even open it, the keywords in the path reinforce the topic, and a clean URL is more likely to be clicked when it appears in results, shared in a message, or printed in plain text.

The transformation rules

The tool applies a consistent set of rules. Letters are converted to lowercase so that the URL is canonical and you never end up with two addresses that differ only in capitalization. Spaces and any runs of punctuation collapse into a single separator, so multiple spaces or a stray comma do not produce doubled or trailing separators. Characters that have no place in a clean URL, such as exclamation marks, slashes, and quotation marks, are removed entirely.

You control two of these behaviors. The separator can be a hyphen or an underscore, and lowercasing can be toggled off if you specifically need to preserve the original capitalization. For typical web URLs the defaults, lowercase with hyphens, are what you want.

A worked example

Take the messy title 10 Cafe Tips for Uber-Fast Brewing! with an exclamation point. The tool lowercases everything, transliterates the accented characters in Cafe and Uber to plain letters, drops the exclamation mark, and joins the words with hyphens, yielding 10-cafe-tips-for-uber-fast-brewing. The simpler classic case behaves the same way: Hello, World! becomes hello-world, because the comma and exclamation mark are stripped and the single space becomes one hyphen.

Handling accents and non-ASCII characters

Accented and special letters are transliterated to their closest plain ASCII equivalents rather than being deleted, so meaning is preserved. An e with an acute accent becomes a plain e, an u with an umlaut becomes a plain u, and so a French or German title still produces a readable, recognizable slug instead of one with gaps where the special letters used to be. This keeps URLs compatible with the widest range of systems, since many servers, analytics tools, and link parsers still handle plain ASCII most reliably.

The practical upshot is that you can paste a title in many Latin-script languages and get a stable, portable slug. For scripts that do not map to Latin letters at all, there may be nothing to transliterate, which is why the tool needs Latin letters or numbers to produce a result.

Hyphens versus underscores

The separator choice is not arbitrary. Hyphens are the long-standing recommendation for SEO because search engines have historically treated a hyphen as a word boundary, so red-shoes reads as two words, red and shoes. Underscores have traditionally been treated as joiners, so red_shoes could be read as the single token redshoes, which is not what you want for keyword clarity.

For that reason, hyphens are the right default for public, indexable URLs. The underscore option exists because some platforms, file-naming conventions, or internal systems require it, so the choice is there when you need it, but reach for hyphens unless something specifically dictates otherwise.

Length, stop words, and uniqueness

Shorter slugs are generally better. A focused slug of a few meaningful words is easier to read, share, and remember than a slug that mirrors an entire sentence, so it is common to trim a long title down to its core keywords before or after slugifying. Whether to remove stop words such as the, a, and of is a genuine debate: dropping them makes a slug tighter and more keyword-dense, while keeping them can make the slug read more naturally, and either approach is defensible as long as you stay consistent across your site.

One thing a slugify tool cannot do for you is guarantee uniqueness. Two different titles can produce the same slug, and most content systems require each URL to be distinct, so when a collision happens you typically append a number or a short identifier. Decide on a convention for that and apply it whenever a generated slug already exists.

Common mistakes to avoid

A frequent error is changing a slug after a page has been published and shared; the old URL then breaks every existing link and any search ranking it had accrued, so if you must change it, set up a redirect from the old slug to the new one. Another mistake is letting capitalization or special characters into URLs by hand, which creates inconsistent, fragile addresses. And do not pad slugs with filler words for the sake of length; concise, descriptive slugs serve readers and search engines better than long, keyword-stuffed ones.