What is a URL slug?
It is the readable part of a web address that identifies a page, like “better-sleep-tips” in example.com/blog/better-sleep-tips. Good slugs are short, lowercase and use hyphens between words.
What happens to accents and special characters?
Accents are removed (é becomes e), “&” becomes “and”, apostrophes are dropped, and any other punctuation or spaces become a single separator.
What about letters like ß, æ, ø or ł?
They are written out in plain Latin letters the usual way: ß becomes ss, æ becomes ae, ø becomes o and ł becomes l, so “Straße über Łódź” becomes strasse-uber-lodz.
Hyphens or underscores?
Use hyphens for URLs. Google treats hyphens as word separators but joins words connected by underscores. Underscores are common for file names and identifiers.