What makes a good slug
A slug should be readable, short and stable. Readable because it appears in search results, in shared links and in the address bar, and a human-legible URL earns more clicks than a string of IDs. Short because long slugs get truncated in the SERP and are awkward to share.
Stable matters most of all. A URL is a promise: every link pointing at it, every bookmark and every share depends on it continuing to work. Changing a slug after publication breaks all of them unless you set up a 301 redirect, and even then you lose a little authority in the hop.
Hyphens, not underscores
Google treats hyphens as word separators and underscores as word joiners. free-seo-tools is read as three words; free_seo_tools has historically been read closer to a single token. Google has said the difference matters less than it used to, but there is no upside to underscores and a documented downside.
The same logic rules out camelCase and spaces. Spaces become %20 in a URL — ugly, easy to break when copied, and inconsistent across clients. Lowercase with hyphens is the convention for a reason.
Accents, non-Latin scripts and IDNs
URLs can technically carry non-ASCII characters through percent-encoding, so café becomes caf%C3%A9. It works, but the encoded form is what appears when anyone copies the link, and some older systems still mangle it.
Transliterating to ASCII — cafe — keeps the URL readable everywhere. This tool handles the characters that normalisation alone misses: ß becomes ss, æ becomes ae, ø becomes o, since none of these decompose into a base letter plus an accent.
For a site written entirely in a non-Latin script, transliteration is the wrong call. Native-script URLs are readable to that audience, and Google handles them fine. This tool is built for Latin-script content.
Keywords in slugs: a small factor, not a lever
Having the target keyword in the slug is a minor ranking signal, and Google has repeatedly described words in the URL as a very lightweight factor. What it genuinely helps with is the click: a URL matching the query gets bolded in results and signals relevance to the person scanning.
What actively hurts is stuffing. best-free-seo-tools-top-seo-tools-online-seo-tools-2026 reads as spam to a human and adds nothing for a crawler. Three to five meaningful words is the target — which is what stop-word removal is for, when a natural headline carries too much scaffolding.