Slug generator

What the slug does

It is the readable part of the address, the crunchy-chocolate-cookies in example.com/recipes/crunchy-chocolate-cookies. A good one says what the page is before anyone clicks, survives being pasted into a message without turning into a wall of percent signs, and does not change once it is published.

Hyphens, lowercase, and why

Hyphens rather than underscores. Search engines have long read a hyphen as a space between words and an underscore as a joiner, so blue-widgets is two words and blue_widgets is one. Underscores are here because file names and some systems want them, not because a URL does.

Lowercase. Paths are case-sensitive on most servers, which means /About and /about can both exist as separate pages with the same content and half the links each. Lowercasing removes the possibility rather than relying on nobody making the mistake.

Accents come off. Other scripts do not.

Accents are folded away by decomposing each letter and dropping the mark: Crème brûlée becomes creme-brulee. Latin letters with no accent to strip are spelled out instead, ß as ss, ø as o, þ as th, æ as ae, because those spellings are settled and the same wherever the letters are used.

Cyrillic, Greek, Arabic and CJK have no such shortcut. Turning привет into privet is transliteration, it needs a per-language table, and the tables disagree with one another, the same Russian name has several accepted spellings in English. Rather than ship one and be quietly wrong, the tool drops what it cannot handle and says so instead of handing back an empty box.

The better answer for those languages is usually to keep the letters. Every current browser handles a Unicode slug, and a reader of the language can actually read it. That is what turning off “ASCII letters only” does.

Length

There is no technical limit worth worrying about, and the specific numbers that circulate about slug length and SEO are folklore rather than published rules. Short enough to read, long enough to say what the page is. The limit here is optional and cuts at a word boundary, because a slug truncated mid-word is worse than a slightly longer one.

Changing one later

Every link to the old address breaks unless you redirect it, including the ones you do not know about, in other people’s bookmarks and messages. If a page has been live and linked to, a better slug is rarely worth the breakage. Set up a permanent redirect if you change it anyway.